prepaid - change plan - overpayment
I own three ATT prepaid lines with multi line discount. Yesterday I changed two of them from a 6G data plan to 1 G data plan which cost less. I was charges additional $259 and $17 for each of them for the prorated fees for August. I already paid full amount for August for 6GB data plan services on August 5th and now after 10days I am paying additional 40 dollars for chaning the plan. I called customer service and they blamed me for not knowing this. I am really disappointed with this not being communicated when I made the payment (I understood that I will pay the prorated fee for the new plan and receive credit for the previous plan.) Now I ended up paying $55 and $ $52 dollars for a 1GB service with a multiline discount. How should I understand this?
The customer service representative offered $10 credit as a courtesy