Customer 41 rude

Customer came in to complain about his bill. He said me specifically upgraded him and charged him $180 when he was supposed to be charged $120. So I look into it. Their are no receipts on his account from a corporate location so I couldn't have upgraded him. Checked the account notes because I don't remember the guy it was over 2 months ago. Turned out he requested a plan change and that gave me 3 options. Change it today and have him pay a double bill. Line it up with his next bill cycle giving him his same limited package for the rest of the month but avoid all proration. Or previous billing cycle. Some proration but only half then current day changes but he can increase his plan limits immediately to avoid additional charges. For going over his limit (the last option is against policy unless mistakes were made and need to be corrected) so he had a choice predate plan 5 days and charge $180. Change today and pay around $240 or next billing cycle but get over charged $120(+$15 so far but with 25 days to enquire more charges estimating over $75 more if his usage didn't change totaling $210 ish) so obviously we went with the cheapest option. This transaction yielded me no pay, no commission, I benefitted none from this plan change. He comes back in all pissed yelling you took money from me, your steeling from me, you need to pay the difference on my bill and make it $120. I'm like fuck you. I did what you asked. I gave you options. You selected one and received the charges. So he's bitching and yelling so I get him on the phone with billing because we are not customer service we are sales. You don't go to a car dealership to replace a part when it goes bad the same way you don't go to a phone store and fix billing "issues" I did it out of courtesy. So they explain the same thing to him, you needed it right away, it was either pay $60 more or $120 more he saved you $60. The customer hears he made you pay $60 more and continues to bitch saying that the billing department on the phone said i charged you more rather then when they actually said (they were on speaker). So I flat out tell him we have no options they are valid charges you have to pay them. So he wants to speak with my manager so I let him and he tells him the exact same thing I told him and that the billing department told him. Yet he still complains. Some people have some nerve.