MTN Kenilworth Centre

I took out a contract at MTN Kenilworth Centre months ago. In addition, I purchased 1GB data. MTN has since given my son 500MB daytime date & 500MB night-time. Why would i purchase night-time data when we have unlimited wifi at home. My son has been back to Kenilworth Centre several times, was told they would resolve but nothing has been done. I've sent emails, nothing has been done. I've since had to purchase monthly 1GB @ R149 every month. No-one is interested in resolving this ongoing problem.