Just email them and tell them that the descriptions of local rate or national rate are misleading and can no longer be used and neither can they remain silent on call costs. In other words they have to say that calls to 0845 ... cost upto 4ppm from a BT landline and more from other providers.
In the email to them quote the website addresses I've listed in
this
thread from the ASA (Advertising Standards Authority)/CAP and OfCOM websites which indicate that the descriptions of local rate and national rate are misleading and that they have to mention the actual cost of the call.
Do not mention that technically ASA/CAP guidelines on the use of such numbers doesn't cover websites unless it was an advert. Just basically quote the three website addresses for them to clarify that in fact they can no longer use the misleading descriptions nor remain silent on the cost of the call.