Contract phone

<p>I took contract phone in Dec 2014, I paid R200 monthly instalment in to May 2015 which is R1000. I paid R600 then my contract was suspended if how I don't know. I never received airtime since then. To.my surprise when I ask Vodacom today 26/5/2016 if how much is my balance I want to settle it, I was told to pay R3600.00. I am so confused if why must I pay such an amount offwhich they stopped airtime in April 2015? I NEED A CLARITY ON THIS..... </p>