Unlike the conversion of a standard telephone line, installing ADSL on an ISDN line requires the removal of the ISDN service during the ADSL installation process. Please verify the type of ISDN service that you currently employ, with BT if necessary, prior to ordering ADSL as the process and charges for Home/Business Highway ISDN differs from those of ISDN2.
Home/Business Highway or ISDN-2 - Customers wishing to convert from Home/Business Highway or ISDN-2 to ADSL will be required to pay an additional fee of £42.55 + VAT (£50.00 inc VAT) to remove the ISDN service from the line, will be charged by BT and will appear on your normal telephone bill. To start the process, order your ADSL service as normal, once we have received and processed the order BT will contact you in writing requesting your acceptance of the conversion charge and any other monies due subject to your ISDN contract.
Unfortunately, lines provided by an ISDN-30 service cannot be converted to a standard analogue PSTN telephone line, and are therefore unsuitable for ADSL installation.
Whilst BT have indicated the lead time for installing ADSL on an ISDN line is 7 to 10 days, this is an approximate lead time only. The lead-time can be affected by the speed with which you provide BT with signed acceptance and how quickly BT processes your acceptance. During this period, we will endeavour to keep you as informed as possible about the progress of your order.
Please note: Users converting from ISDN-2 or Home/Business Highway to DSL will only be able to retain their primary telephone number/line. Any other numbers/lines that you may have associated with the ISDN service will be reallocated to other BT customers.