Cell c complaint

My name is Kagiso Ramatong I bought a device at cell c on the 1st of this month December at Newtown branch I was assisted by the lady called Dikeledi since I bought the phone I cannot go use internet the only thing I can do with my phone is to call and receive calls only but not the internet I have been to the store several times in which I have had 2 sim swops done but still the sim card is not able to access the net if you insert another sim in the phone the internet works pretty well just not the one issued by the store I have called the call center technical department and sent numerous queries but till today I have not received any help please assist as I cannot pay for a device that I am unable to use fully