Curly handset cords, old or new, have a nasty habit of getting tangled up.

It's quite easy to work the twists out but the coils rarely seem to lay properly afterwards.

A way of at least improving things is to wrap the cord around a metal bar and then pour a kettleful of boiling water over it.  This is also a good chance to clean it by attacking it with a soapy nailbrush.

After that run it under the cold tap and remove the bar.

Some people apply the heat with a hair-dryer or hot-air gun and some put the cord and bar in the oven at 100C for half an hour.  I've never fancied the former for fear of going too far and melting the covering rather than just softening it, and I don't trust my oven thermostat that much either.

People have also claimed good results from placing the cord on the parcel shelf or dashboard of a car that's parked in the sun.  Opportunities for that are somewhat limited in England though.