MTN the worst service ever

I struggle with signal. If I make a phone call or received one the line is very bad nobody can hear me. My emails don't want to open or the attachedments don't want to download. I must restart my phone all the time to receive whatsapps. Can't go on the internet it is very slow or it give me an error.

I called MTN on Tuesday they said they will change the network then I must switch of my phone for 30min then it will be fine so I did it when I switch on my phone after 30min it was the same as usual no signal.

I Phoned again the lady talled me the internet wasn't connected she will connect it then I must switch off my phone for 5min so I did it again after 5min I switch on my phone agian. It was the same nothing changed.

I cant go on like this because they take my money every month for the contract but I can't use my phone.