My email address used on other clients' accounts

MTN does not validate user email address to ensure that the provided email address belong to that user. For months now, I have been receiving other people's correspondences. When I reach out to customer support, they tell me the issue is resolved but a month later, it happens again. This is a simple exercise for vetting customer information and if they claim it is resolved, why does it keep happening. I am super annoyed with MTN for this.