Terrible service

Terrible service. I renewed my contract on the last day of January and paid in store. My number got blocked in the second week of February as MTN claimed that my account was in arrears. The payment I made in store does not reflect on my statement and I was asked by MTN to share the proof of payment for that transaction. I did this the day my number was blocked. We are in March now and MTN just emailed me asking me to send it again. I am still being billed for the month of March (as per the MTN app) but I haven't been able to use my contract SIM in almost a month. I asked to cancel this contract but they're telling me that I can't cancel it until the outstanding fees are paid. I've had contracts with this number for more than 7 years. This is unacceptable.