Paying for something I don't know

<p>Someone used my cell phone number after they had hacked into my cell phone number on the 04 January 2017, then I got an SMS from Milayds and Sheet street saying I had purchased goods that worth R300 from each company but someone had used my accounts without my concern. Then I rushed to Vodacom and did a sim card swop since they had hacked into my cell phone, then Milady's and sheetstreet said I should do an affidavit to prove that am not lying, and both the accounts were paid up, and they kept on calling, sending SMS's saying I should come and pay. Then I told them I won't pay the accounts because am not responsible for the purchases that have been made, because they were made without my concern, so can you please help me with this case.</p>