Welcome to the BT Residential Customers forum
As you are a business user, please could you post on the BT Business forum at http://business.forums.bt.com/
BT do not permit you to use a residential account to run a business, as its against their T&Cs.
This is a customer to customer forum only,
This is where customers help each other get the most out of BT products & services.
Anything you post here does not go to BT. Although the forum is moderated by BT, not all posts are read.
Everyone else here, are just BT customers, so cannot help with your problem.
The ombudsman will not deal with individual complaints.
If you moved from another service provider, then they may not have released your old number to BT.
The problem with a domestic line is that you are the bottom of the pile when it comes to priorities. The service is provided "for your own personal use and enjoyment". BT aren't interested in how much bisiness you are losing.
If you paid extra for a business line, then you would be a higher priority.