I don't want this phone anymore

I upgraded to a new phone, the new phone takes a nano sim card. Went to do a sim swap on Tuesday, till today sim swap not working. This means for 2 days now I am not reachable. Called 135 they said sim swap shows as successful. Called the store, the store Manager Karabo is very rude. I want to just part ways with MTN. I want to return the phone it less than 7 days.

Where can I take it?