BB 9720 - FAULTY PHONE

My phone just switches off & the connection for my charger is faulty. I took my phone to someone in Ballito who fixed blackberry phones & he said this is a very common problem with this phone. I kept on buying new chargers thinking it was a faulty charger. (I must say that I was impressed with the suppliers of the chargers as they freely changed the charger.....why can't blackberry do the same). My complaint is, how can I be locked into a contract for 2 years with a faulty product & then be expected to be without a phone for 15 to 22 working days, (already phoned their call centre & technical centre) whilst it goes in for repairs. I should be given a replacement phone &/or be allowed to upgrade my contract so that I can change the phone. This is absolute nonsense & I cannot believe it is allowed. Where is your 'keep your customer happy' Blackberry. What now???