Supermarkets, football clubs, airports and major utilities companies are still using costly 08 numbers two months after they were banned.
Fair Telecoms Campaign has named and shamed hundreds of companies dragging their feet over the new rules, including National Rail, Heathrow Airport, Lidl and Tottenham Hotspur.
New regulations came into force on June 13 this year, prohibiting use of numbers not charged at the 'basic rate' for contact from consumers.
Calls to all numbers beginning 07, 08 and 09 are not charged at the 'basic rate', as special charges are imposed, so companies have been told to offer 01, 02 or 03 numbers.
Dave Hickson from the Fair Telecoms Campaign said: 'We want to get rid of these numbers once and for all.'
Consumer watchdog Which? said that people should not be expected to pay a premium to ask a question or complain.
Executive Director Richard Lloyd said: 'If they haven't already all companies and public bodies should now do the right thing by consumers and drop high rate numbers without delay.'
The 084 and 087 lines can cost up to 15p a minute from a landline and 41p from mobile phones.
Most leading firms including Sky and Morrisons have switched to basic rate 03 numbers, which are normally included in phone users' monthly calls allowance.
Any company which fails to comply with the new law and still offers a premium-rate number for their customer service line will be putting themselves at risk of court action.
Customers will be within their rights to take such companies to court and successfully reclaim the excessive charges made to them.
Trading Standards are also able to get involved in bringing companies to justice.
