The company is using 0844 numbers, which offer local call rates per minute from anywhere in the UK. The transition will be complete by December 1.
The move comes ahead of the February 2008 change in charging structure for 0870 numbers by telecoms regulator Ofcom.
Holiday Taxis sales and marketing director Russell Parr said: “We are the first transfer company to make this move and it continues our commitment to providing a quality service to the travel trade.
“We want to be ahead of the game before the February change comes into play to give our trade partners time to get used to the new numbers.”