Unacceptable behavior from Vodacom won't reccomend to anyone to use Vodacom

I have baught a phone by someone about 3 years back and it working perfectly since i baught it But about a month ago it just says no signal and i was at the i store and they said cell ce blocked it. So i went to cell c and they said no vodacom blacklisted it so we dit the whole unblaclisting process with vodacom and we recieved a mail after 3 days that the phone has been unblaclisted and the phone should work in 48 hours. We then waited another 3 days and still it doesn't work. So i went to a vodacom store and they resetted the network settings and the phone worked after an hour the phone stopped working again. We contacted the head office and explainned to me they have blocked it again due to the previous owner that didn't pay. I baught the phone cash 3 years ago and it was working perfectly for 3 years now they say it's been blocked and now they expect me to pay tge other guys bills i have lost alot of work due to my phone not working this is unacceptable i have the origanal box and everything and i even showed them. The person at the vodacom shop said they cant expect me to pay what that guy owes and i agree the phone was working for 3 years and then it doesn't work is there someone who can help me from vodacom because i am loosing alot of work due to not having a phone