Liable for wrong vodacom contract

November black friday I registered a 10 gig contract for R99 per month for 12 month. When I go to the store the following week to collect my sim card I was given a wrong one, then they phoned me to come to collect the right sim card. Only to find that the sales lady registered a contract for R149 for 12 months which is what I did not sign for. She also captured the wrong playdate to debit my account. Each time the debit order bonuses vodacom charged me 100. Now vodacom(alliance) phoned me and said I must pay areas of +- R1300 for non payment.i told vodacom that they have me the wrong contract. Vodacom said I must go to the store to talk to the sales lady, only to find that she resigned and they said there's nothing they can do I MUST PAY THE AMOUNT OR I WILL BE HANDED OVER. This is bad service because now I have to pay for what I did not use and sign for. Please assist. Vodacom ***