Pinnacle Financial Group Harrassing Myself and My Family Also Charging Fake Fees Minneapolis, Minnesota

Pinnacle has been harassing not only myself, but my family about a cell phone bill that I had with ATT.  I broke my contract with ATT, and wasn't aware that I would be paying fees for 3 of the phones on my plan.  I thought because they were eligible for upgrades that the contracts were up.  I was wrong and was slapped with a large fee and even got taxed on the fees from ATT.  Since the bill was so high, I was forced to setup a payment plan to pay them back monthly.  I have made payments to them faithfully every month not even being late on one payment. Then all the sudden my daughter, husband, sister, and myself all started receiving harassing phone calls from Pinnacle. They are calling sometimes 10x a day. I answered the phone the first time and tried to explain to them that I was making payments already to ATT, but the person on the other line barely spoke English and just kept telling me to give them money. It was beyond frustrating because they couldn't understand me and I couldn't understand them. I finally gave up and hung up on them and haven't answered a call since. The other day I received a letter from them showing a balance of more than what I owe to ATT plus what is listed on their bill as an "AT&T Fee" of $55.80. I checked ATT's website and their balance is correct to what I have as what I should still owe them. There is no fee at all listed. These people are trying to scam me and harass me into paying more money than what I owe plus a fee that is not from ATT like they claim. I'm afraid this will go on my credit report. I have no idea what to do.