Yes its a mobile number,and charged accordingly.

Code: 079 731    
Type: Mobile
Use: Mobile Orange
Operator: Orange
Tariff Band: Orange Mobile (fm4) (inc VAT)
Service: Mobile

Dave wrote on May 12^th, 2008 at 7:45pm:

... Not necessarily - I went through this one many years ago.

Because of number portability there is no guarantee as to which network a number is connected to.

If like me you benefit from cheaper calls within the network, e.g Orange-Orange, there is no guarantee that a 07973 number will still be an Orange number. It is unlikely that Orange would have ported its customer services number onto another network, but the prefix provides no assurance of the cost of the call.

If you want to know which network a number is actually on, the only way to find out is to ring it and ask, or wait to see what comes up on your bill.

I find this unacceptable, but what is the answer?

Should number porting be prohibited?
Should network operators not be allowed to encourage referral business amongst friends by allowing cheaper "in-network" calls?
Should Ofcom require the mobile companies to provide a free "which network" enquiry service?

greyjaybee wrote on May 13^th, 2008 at 6:58am:

That's because the number you've quoted is 07973 100450 which is PAYG customer services. The number from an Orange mobile for this is 450.

Calling 150 from an Orange mobile gets you to pay monthly customer services, which is 07973 100150 from a non-Orange phone.

If you called 150 from a Orange PAYG phone, I'm would be surprised if it's free.

greyjaybee wrote on May 13^th, 2008 at 6:58am:

Unfortunately Orange uses its own mobile numbers for its call centre. The cost of calling them is usually higher than 0870, especially from a landline, and thus I think it's certain that the rake-off is higher than had it used 0870.