Changing providers has nothing to do with the BlackBerry Desktop software working on your computer. I recommend making sure you have the most up to date version of the software and even to completely un-install it and re-install it.
I didn't think it should either, but it only started to malfunctioned after I had changed. I also uninstalled and reinstalled newer version of software to no avail. Perhaps there is a setting on my phone I have not yet discovered. I am old. It simply does not even recognize my device, yet it is connected as the phone charges while connected.