Bad service I received frm vodacom

I app**** a phone from vodacom thinking they come with two sim slot only to find out that vodacome's phone they do not come with, after receiving phone I returned it back the courier guys when I asked for receipt they said they do not give receipt so they took the phone tomorrow received a sms from vodacom saying that they have received the device back after few months I started receiving phone calls from debts collectors saying I own vodacom at branch they referred me to call I called and send emails no respond frm vodacom my name today is listed no one frm vodacom wants to assist me