[Mayson]

I agree with you. It is possible, and I explained how. You also have 2 other possible methods that I forgot to mention.
1) an insider in the service provider who has the privileges to divert calls
2) draw up a fake warrant demanding that the service provider divert calls without the owner's knowledge to a particular number and send it to the provider's legal department.
Apart from those methods, I can't think of another way. Perhaps you could share how your "people" are doing it ?