Where a telecoms company offers telephone service to retail customers they must charge calls to 084, 087, 09 and 118 numbers as Access Charge plus Service Charge.

Where a telecoms company offers telephone service to business customers they have the choice of charging as Access Charge plus Service Charge, flat-rate pricing or some other scheme.

Given that some callers calling RS will be subject to Access Charge plus Service Charge pricing why would RS seek to withhold a vital piece of call charge information that those callers will need?

RS has either misunderstood or is in denial about the true nature of the call charges for their 0845 numbers:
www.nidirect.gov.uk/the-cost-of-contacting-08-and-03-telephone-numbers