MTN - never take a contract out with them.

Every month my mother's contract gets suspended, and she pays every month on time via EFT, and every time she must take off from work to go to the bank to get the proof of payment to take it to MTN so that they can unblock her phone. This has been going on since February 2020. Every month she must struggle with this. Her phone has been blocked now twice in one month!!! Why must she struggle to get this sorted out? I would like to know can she cancel her contract with them? She has been with them for ages. This is really pathetic. Shame on you MTN!!!