You could get the NTL retentions team to offer free call baring of premium rate and operator services numbers by saying you are switching to Bulldog as Bulldog offers this service free. NTL is bound to give you free call baring from then.
BT's call baring service is crap because when you bar premium rate numbers, it also bars national,mobile,0870 and international direct dialled calls which is stupid and very outdated. And the service costs £1.75 per month. Alternatively, you can download BT's modem protection facility at
www.bt.com/privacy , I used BT modem protection when I used Telewest's dial up service.
Furthermore, its not BT's,NTL's or Telewest's fault that you have to pay for this scam. When you call a premium rate number, your service provider is charged first and the service provider passes this charge onto you plus a small charge(Between 6p and 70p) depending on the type of number you are calling. If you want your money back, you could try contacting ICSTIS which deals with premium rate number misuse. Once a complaint has been raised they'll contact the operator which leases the premium rate number and the user of the premium rate number will have their revenue share privilage taken away and eventually you will be refunded.
You can't just call your service provider and say you've been scammed when you find a premium rate number as you have no proof and the service provider doesn't have much power to withhold any payments to the operator who leases the premium rate number and you should really contact ICSTIS.
There is also another con where scammers use 070 and 0871 numbers. For this type of problem you will need to contact Ofcom on 0207-981-3040 Monday to Friday 9am to 5.30pm. Usually, people would find a missed call on their mobiles or landline with an 070 number as it poses as a mobile number which it isn't and if you return the call, it some kind of answering service which keeps you on hold for ages whilst charging you 50p per minute. Now the 0871 number scam is a problem were people find a message on their answer machine telling them that they have missed an important phone call and tells them to call an 0871 number, when they call the 0871 number, you are placed on hold forever and you can be charged between 5p and 10p per minute from a standard BT landline.