blacklisted for no reason

DISGUSTED in vodacom.went saturday 20/06/15 to fochville vodacom chatz to get a copy of purchase for my samsung s4 thats on my wifes account to send in for repairs on a cracked screen.so weve been told that our imei number is blacklisted and the reason therefore is *****.but my wifes account is up to date till may 2015.neither could they tell us who blacklisted the phone.weve been told the phone was blacklisted on july 2014 but i have still used the phone up until february 2015.how can this be possible?i held vodacom resposible for this and if its not sorted out in 2 weeks i will force myself to an attorney to take it further and will sue the responsible.