Network problem in the afternoons

I am very annoyed with MTN network,I have been their client for over 4years with issues at all, I recently upgraded my contract with them, which I do every 2 years but I regret upgrading this year. So in January I got a call that I was due for upgrade and I was happy to do so, ever since the upgrade was done I have network problem everyday in the afternoons. Around about from 5pm I just can't use internet.worse part this is the time when I really need network hence I have to help my son with school work,,, I have sent emails to MTN with no luck. I went to their branch in Davenport Durban, and the guy that helped was not helpful at all . Instead he told me I must try simswap, when I asked him if it does not work how will this issue be resolved,he did not have an answer because it can't be the problem with the sim card hence network is working fine during the day,but did not seem to understand my point until I asked for the manager,and I was told to contact the call centre when I am at home so they can check the tower I am connected with...I got home as usual the network went off after 5 I contacted the call explained my problem I was told the tower I'm connected on is off and it gets busy in the afternoons they will and put my number on Auto connect,okey but still the problem is not solved I called again and took ref the second time SMC*** was the reference for the call....so I need to know since the towers goes off that means I am paying MTN for data that I can only use during the day, what is MTN doing about this problem,as I was told I am not the only one with this problem in my area, if this matter can't be resolved can I get help to cancel contract with them without paying cancellation fee? ..mind you my Vodacom works fine my husbands Telkom has no problem. Yet MTN has problem. I don't think this is fair.