No reception

This is not a complaint per say, but I am not sure how to deal with this. I have had an MTN contract for years and have had no problem to date. I , however, am having serious issues recently. My phone often has no data reception and says \Not on registered network"when I try and use it. I am currently in Durban on a business trip and I am highly frustrated that I am getting no Internet connection with MTN. I am getting the same problem in Pmb. These areas should NOT be having such problems. I am being left with no contact with anyone I am supposed to bensure contacting due to this problem. My contract is ended towards the end of this month and I am seriously thinking of getting a contract with another service provider as MTN is leaving me stranded due to network issues."""