misinformed

I took my cellphone to Mtn festival mall bcoz its just went blank while charging it. I was given a n agreement form to fill and signed and the sales person didn't mention anything about paying for service delivery and it was not on the agreement form I signed. Now Mtn technical doesn't want to give my phone back without this R330 for service delivery and I refused to pay it bcoz I was not told about it before hand, so they told me to take it up with the manager at mtn Festival mall where I took my phone in. I called the manager named Victor to explain to him what happened and he told me they didn't know about the R330 when I took my phone in, where as Mtn Technical told me the rule of paying R330 for service delivery was effective from 1st November 2014 and I took my phone in 3rd of November 2014. I emailed Mtn technical yesterday and they told me my phone is quarantine bcoz I didn't pay the R330 in 90 days. I want my phone back bcoz its not my fault I was not told about this R330 upfront and I was given a old agreement form.