Cinemax was supposed to be $5 monthly, yet its $15.00???

My brother was supposed to have Cinemax service added at a 12 month promotional rate for $5.00 a month. Yet, when he just got his bill, he is being charged $15.00 a month. He has the chat transcript where the employee said it would only be $5.00 monthly.

Is there anyway he can have this resolved and have $10.00 deducted from the first bill? Or what does he have to do? This is VERY inconvenient for him so please help.