If the phone synching has not worked since the SIM was swapped, it is the SIM.
If you have SIMs all provisioned properly, you can swap them as much as you want without needing to reactivate the device. As long as the SIMs carry the BES data component, the BB doesn't care a fig for which SIM it has, or the phone number or anything else. It just needs the data plan...
: Infrastructure Architect, Denver CO