The Take That star made the admission while being interviewed by Williams - who apparently does not own a mobile phone - for his new radio show Rudebox Radio, The Sun reports.
"I own no phone apart from the house phone," Williams said. "I just use everyone else's, I think I've used yours, Gary, I think I've used Jay's (Orange)."
Barlow quipped: "I was thinking of charging you but I thought that I can't do that again. It used to be a quid per phone call. Can you imagine what it would be now?"
Meanwhile, the X Factor judge also admitted that he regrets not having sung lead vocals on Take That's 1995 number one hit 'Never Forget'.
"The only thing wrong with 'Never Forget', for me, is that I'm not singing it," he said. "We used to divvy up stuff per record and when we first recorded the song it wasn't the stand-out hit that it became, so I said, 'Here you are, Howard (Donald)'.
"Then it had a big mix and it was just a different record when it came back, I was like, 'Ey up'."
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Watch Take That's 'Never Forget' video below: