Bad service from branch and head office

I hade an upgrade at mtn they was fast to help me and les than an hour I hade my new phone SONY EXPERIA Z3 I went home with my phone but couldn't use it because it was still offline so I waited till the next day still nothing I hade the phone tree weeks until my debit order went of before I could use my phone after mtn took R200 more than what was to go off.. I was happy with the phone so didn't mind the R200 I hade use of my new phone for not more than two weeks when it got software problems I went back to the branch and I was told to bring in the phone with box and charger and my phone will be replaced the next Friday well now that's two months ago still paying for a phone I don't have and I cant even use the simcard because it dosnt fit any other phone I have, the sim is to small to fit anything... every time I do get a chance to go back to the branch I hear a new excuse and excuse and excuse im fed up now someone need to do something I have send a couple of mails to mtn butt didn't even get a reply....