Cell C Pro-rata account

I was on a pro-rata Cell C fiber account. I recently moved from Cell C to another internet provider as the support I received was appalling. My account originally was with Iconnect but they sold to Cell C and my account was stuck between the two companies. On the 20th of June 2019, my fiber line was released and on the 21st of June 2019 my new ISP took over my internet connection. So as I was always on pro-rata I paid for 21 days of internet usage and not the full amount of R899. I was told all original agreements I had with Iconnect would stay the same when they moved my account over and I had not agreed to any changes on my account. Now, 1st July I get another bill of R261.00 that I owe Cell C.

I will not pay you that which wasn't used, I have proved I was moved as of the 21st and since I hold no agreements with you I will not pay the rest. Your company is as useless as your support. I wish Cell C (nice an awesome company) a slow and painful bankruptcy as you guys deserve it.