Errors in billing

When I got the service I had to pay a $50 deposit for the equipment and a $10.99 fee for for the first month of service it said that I was supposed to be able to get two months of service free when I paid the $62 on the app it said it didn't go through the first time so I paid it again which gave me credit two months later I'm now being charged late fees and $60 charge for my service this month after being told in my bill that I had credit all the way up until this month I don't understand this is crazy

what's even more crazy is there charging me 90 something dollars when I had $60 credit and I've only had the service 2 months