Bad service from Rain

I had a month-to-month contract with RAIN, and it worked perfectly for three months. However, I then started experiencing connection issues. Despite numerous calls for assistance, they couldn't help me, and I had to restart the service every time I used it. I decided to cancel my contract because I had already paid for the month, but they refused and said I must continue with the unreliable network for another month before I could cancel. Now they are threatening me, claiming that I owe them money and that they will add interest if I don't pay. Please assist me with this issue