SIM Swop 2 days and still nothing

my phone was ******, i went to MTN to get a new sim card with my old number, service was good but i'm still waiting for my sim card to be activated... i've gone to two branches and each time it's 2 - 24hours it should work. My number is *** and i'm in sales so it's costing me more oney not to have the num,ber working, they want you to open a contact and that they fast but when it comes to fixing an issue nothing gets done. Can i Cancel my contract and go to a network that works???