Blacklisting

Hi my cellphone which I own for more than 7 months has recently been blacklisted after buying this phone cash from someone who didn't want it. The phone came sealed in the box with everything. So I been running around trying to fix this issue went to Vodacom they said mtn blacklisted it went to mtn they said they can't blacklist it now I don't know how to fix this issue because I payed alot for the phone. R15000 isn't a small amount of money and I expect alot more help knowing that I have a business contract with Vodacom and the only reason I bought this phone cash was because my previous phone was ******.