From 26 October 2015, financial services firms will be banned from using pricey 084/087 numbers for existing customers.They must  be charged no more than the standard rate of geographic numbers  01, 02, 03.

But the Financial Conduct Authority's (FCA) new rules won't apply to non-customers where 084/087 rate numbers can still be used.

http://www.fca.org.uk/news/fca-finalises-rules-on-complaints-and-call-charges

That's the same as the situation for retailers, traders and passenger transport companies in relation to Regulation 41 of the Consumer Contracts Regulations 2013.

One year later there's a crucial additional component. All users of 084, 087 and 09 numbers are required to declare the Service Charge for their number everywhere it's advertised. Those who are unable to justify this charge must change their number to stop imposing it.

Translation: They will still be allowed to rip off potential customers, but must tell them they are doing so. Those customers will have the option to take their business elsewhere.