The repair centre I believe would only contact you if they needed more information about the problem in hand.
For example, if you described a fault and they were unable to replicate the error then they would contact you for more information
as far as the repair process goes, I BELIEVE they just send you the bag, you write the fault on the paper, send it in , they repair it and then send it back
If the issue was the fact they couldn't contact you. Unless specified as a contactable number then the repair centre wouldn't know who to phone as they don't have access to your details at Virgin mobile/media
How have you got on so far with this
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Virgin Mobile Staff , However, All opinions are my own