AFTER BUYOUT THEY STILL WANT MORE MONEY!!!!

I bought my phone months ago out, I have certificate of ownership, yet they still have the blocking system on the phone, and now I get an email from lawyers requesting R37,000.00 for IPHONE 11, which I bought out and have ownership certificate!!!! PLEASE DO NOT BUY FROM THEM AGAIN!!!! I have report them now to ombudsman!!!!