David Letterman can't use a phone.

The former 'Late Show' host has admitted he struggles to use the telephone now after having an assistant make phone calls for him for over 30 years.

He said: ''As it turns out, after all these years of having someone make my calls for me, I can no longer operate a telephone.''

The 68-year-old television presenter also admitted he is finding it difficult to know how to style his hair.

He added: ''I don't know what to do with my hair, either. But I'll never wear makeup again, so that's no problem.''

However, David is enjoying having leisure time so he can take his 11-year-old son Harry fishing.

He told PEOPLE magazine: ''I love fishing with my son. Any kind of trout fishing where you can stand in the river is just delightful. I don't know what I'm doing, but I can stand in the river. I'm pretty good at that. And isn't that 90 percent of it?''

When the star made his exit from the show last month, he thanked his fans for ''everything''.

He said during the final taping: ''Have you thought about a complete psychological work-up? The people who watch this show, there's nothing I can do to ever repay you. Thank you for everything. You've given me everything.''

The 80-minute broadcast featured many celebrity guests, video montages and his famous sketches as well as a performance from David's favourite band, the Foo Fighters.