Worst Experience of my Life!!!!!!

I bought a new Samsung A5 from Vodacom Woodmead Retail Park in December 2015, on the very same day i collected the phone i started receiving calls from people accusing me of *****ing someones' phone, because the number i was using belonged to a ****** phone, some of the people even saying they are going to report me to the cops. The following day went to the store to tell them the story, found the Assistant Manager, he could not answer me and kept on going to his manager's office for advise, the Manager did not even show his face. He told me that his manager said 'I will have to leave the sim card with them so that they can send it to Vodacom's office somewhere'. He then gave me a prepaid sim card so that i can continue using the phone, and promised me that he will call me in a day's time. 4 months no call from him, i then go to the store, he then says 'have the police arrested you yet'?? then he laughs. I ignored him, The other lady said i must sign on a blank paper 10 times and submit an affidavit, i did that but its now April 2016 i am still without the sim but they keep on debiting my account every month. I dont know what to do anymore with this guys, i regret buying this phon