Customer 3 (bad)

A few months back maybe even a year or so now i had a customer come in, they use to pay us well on selling tablets back then to. I don't remember the full details but i do remember that i had worked out a plan for him and i even talked to my manager on it to ensure everything would go fine. He came in to upgrade his phone, great no problem let me do a plan analysis for you. Most people are willing to wait 10-15 min for that so i have plenty of time and with my experience i can do it in 3 or less, so i finish the analysis and find out i can save him $60 per month on his bill with 3 phones on it. Awesome however i unfortunately work in sales and they tell us all the time save the customer money when you can but don't sell them out of your pockets, make them offers first. So i figure a good line is, Sir today i can save you $15/month and you can get a tablet for each phone on your account with 1GB per month of the cellular data and ill even set the cap so you don't go over. He asks "Does it have any hidden fees i should be concerned about?". I think well none of our fees are hidden, hidden and not reading your bill are different so i explain more, no hidden fees, you will pay $15 per month per tablet, i will have my manager credit your $36 activation fees per tablet and no other charges will be present. You will get $60 off what you are paying now, the tablets will be $15 each totaling $45 and in the end you save $15 per month. Great he accepts the offer and we get him set up, we waved the $240 upfront cost, the $36 credits are applied and his bill is lower. Next month he comes in with his bill saying it has a problem, So i look it over print out 2 of his previous bills to compare and his bill is roughly $16 less. I go over it and ask what is the issue and he said, "You told me the tablets were free and right here i see $15 for each and $36 activation fees". So i point to him the credits we provided for those $36 fees because at the top it says courtesy credit $110 which covers all 3 fees (yes i know the fees are $108 but management always round off, they tell me audit does not like seeing numbers that don't end in a 5 or 0, not sure why though). And i explain that i not once said they were free, that they would be $15 per month and he wouldn't pay anything today for it and you would save $15 on your bill. I show him the bills for comparison and he yells out "No i know what i herd you said they would be free and i would save $15 per month!" I said sir you are saving $15 per month, your end cost from what i think i said and from what you think i said are the same, either version of how that conversation went cost the same, i don't understand why you are upset. So he freaks out and wants to speak with a supervisor, my manager just got in literally less then 10 seconds before he request that so that was lucky timing. So i tell him sure one moment, I grab my boss let him know whats going on and he is as confused as i am. He gets settled in real quick and starts helping this guy, since hes helping him and we have a line coming in i help the next person and i'm only about 8 feet away so i can still hear and see whats going on. So i begin to help my customer and i hear him explain to my manager his side of the story, he does not know my side yet so he only knows what the customer is telling him. After explaining to my manager whats going on i here him say to the customer "soo... what your telling me is he promised you $15 cheaper per month and your paying $15 cheaper per month and their is a problem?". I am thinking awesome so i'm not missing anything this customer is crazy, and the customer starts yelling out "I'm going to hit him i seen you run in the back come out here so i can beat your ass" and i'm thinking to myself umm i am literally 8 feet away from you in the same room and can see you and you can see me why are you yelling to the back. So whatever i finish up with my nice customer while he deals with this dickhead. And when my customer is done with and the store is about empty now he leans over to my desk and request to talk to me again, so sure, i go over to where my supervisor and him were working which was literally the station next to me and he starts throwing out threats and i'm thinking to myself how has this guy made it to his ripe old age of 50+ in his life without going to jail. So i just tell him sir, i said i saved you $15 per month, your saving $15 per month, i said each tablet was $15 per month each but you would still save money monthly. And everything i said came true. Even if your side of the story is true at which i told you the tablets would be $0 per month which its not, the end result at which i said would be a monthly savings of $15 still applys and you even agree $15 is what was agreed upon for your monthly savings, if the tablets were $0 then you would be $60 less not $15 and you yourself said $15 was the agreed upon amount of savings. I see no problem here and i don't understand why you are upset. So he flips out more and storms out of the store after making a few more threats, so i note his account his behaviors and state the threats he shouted in store towards me. The next day we get a call from our district manager saying to check his account. God damn customer service replied to my notes stating the customer had a bad store experience, gave him $1300 to cover the $600 in tablet cancellation charges and an extra $700 for his inconvenience. So this guy in 2 days got 3 tablets worth $300 each for FREE saved $60 on his monthly bill and got an extra $700 for inconvenience. So i am pissed about this situation because this basically tells me the company i work for values a bad customer so much that he can make threats to your employees, waste your time and resources and gets rewarded for it. I think this situation is insanely stupid and yes this is a true story, tell me what you think, do you think i was wrong for saving him $15 on his bill and giving him 3 tablets or do you think the customer was right and deserved the $1300. He was aware that he could save $60 per month still but i made him the offer of $15 and 3 tablets so i did not force him into it.