sbiddle: There are many ways in which this could happen and without knowing more it would be hard to give an actual answer.
Do you have internet access right now with a new provider?
andrewcnz: When my internet stopped on midday Friday I thought it was the router so I got another one , still no good so I then rang my ISP snap. It turns out that another provider has got the line now. How does this happen I never asked another provider for an internet service. Now snap have to try and get it back. Oh dear how can this happen!?
Kyanar: The new provider isn't Slingshot is it? They have a bad reputation for what the Americans call "slamming" (where they call you up, and during the course of the marketing call collect just enough details to change your line then do so without express permission) - just look at this thread and this thread.
Your friendly Southern Geeky Fellow :P
PenultimateHop:nate: All you need to swap is the name on the account, account number and address. Wholesale are very picky about this, so it needs to be exactly right - someone must've taken a copy of your Snap bill and given this to your "new" provider.
Time to find a new industry!