System Always offline

I was called by RTT 3 weeks ago telling me that mtn is giving me a new upgraded LTE SIM card which has better connectivity and it will be delivered to me, I received the SIM card on 28/8/2015 and have been trying to do a sim swop since that day and whenever I call the call centre I give them my details only to be told to call after an hour or 2 because their systems are offline. What is the use of giving customers new sims if they can't even do a sim swap? I've been with this pathetic network for ages and this just annoys the living hell out of me! I am even on the verge of porting to another network since your systems are forever offline!