Bad customer service from the store manager

I purchased a cell phone @ pep cell tshwane Reginal mall in pretoria the Phone takes a Mtn Sim so my daughter put the Voda Sim then the phone blocked and they never explained to me that the phone only use Mtn simcaed now they giving me attitude. They don't wanna help me with the blacked phone and it's still new... I call the store manager and she gave me attitude also and handed up the pho e and she was so rude...