I am being scammed by Comcast Business

Two months ago after years if using service my rate was hiked up for such low speeds so i voluntary permanently disconnection form signed with showing that i owe 0.00 on balance since i had autopay and billing was ok. Well two months later Comcast Business is still billing me now bill up to 500 dollars every month new bill even though i have signed disconnection form . This is terrible i am being scamed they’re trying to ruing me credit i will sue them for this scam