shellco credit i had a lease agreement with gmac for 2007 sierra then lease expired and i returned the truck i still owed them money so gmac gave my account to shellco credit they phoned my several time i told them vancouver, British Columbia

i leased a vehicle from gmac then i returned it i still owed money on it so they send my account to shellco credit. They contacted my few times i told them i cant pay at this time as i could not afford it at time but they kept on phoning me so finally we agreed on 4000 which i will borrow from my family members so i did and i paid that amount which they said would be final payment and my account would by paid but instead they took the money and now gmac trying to collect from my again when i phoned shellco they are lying and saying this is not true i was just wondering if any body can give my any suggestion what i can do