HT3743 Contract of 3 years with bell honored iphone paid in full now error 1015 WT

Bought a new phone, so gave my old iphone 3g to my son. Since he is with a different carrier, Telus (i was with bell, contract honored, phone paid in full) I had to unblock it for him to be able to use it. I went to a mall, and had it unblock in a shop. Now error 1015!!! After reading other posts related to this issue, I am trying to understand but really don"t: So paid the phone (over the 3 years contract!!!!!), but can"t do what I want with it??? Is it still Bell"s property???? Is that legal? What can I do? Even if I kept it let"s say, and went abroad, I"d still need it to be unblock (GSM) for me to use it!

Can Anyone tell me something about this problem? And who should I contact? Bell???

Thanks a lot!