U.S. CELLULAR overcharge no customer service lied JANESVILLE WI Wisconsin Nationwide

i've been a customer of U.S. CELLULAR for a few years. my first problem came when I paid my bill by droping it in their box. I was charged a late fee for them not getting it. They said they were not reponsible for bills put in their box. While talking with some people about U.S.CELLULAR , I brought up the late fee. A woman said she was sorry, I asked why and she said it was her job to empty the box,open the envelopes and attach payment to statement and throw the envelopes away. She said she threw some away without opening them. I asked if U.S.CELLULAR knew this and she said yes,but U.S.CELLULAR denied this. We got a hot spot a couple of years ago to replace using dail-up internet . The first few months were okay,but now we keep gettin overcharged. I've called just to hear them say  can you prove you are not using this amount of data. I said no and was told I would just have to pay what I was billed. I could change provider if I didn't agree.,so I did. but U.S.CELLULAR woulded let my phone number to be ported for (5) days so I would be in another pay period and could be charged for  another month. MY bill went  from $78. to $97.70 when i CANCELLED my service with them