The money expert suggested that the price of the average 4GB phone deal has halved in the past five years.
"If you haven’t sorted out or changed your mobile phone deal, you are likely paying way too much”, Mr Lewis said on an episode of the Martin Lewis Money Show Live.
"My big question would be, ‘are you paying over £10 a month?" If so, why?"
Mr Lewis found that one third of his responders on Twitter spent over £30 per month for their mobile phone – although Twitter polls may not be as representative as those done by professional polling agencies.
Another third spent between £10 and £20 per month on their phone.
Quick poll (for interest before my show tonight): How much do you typically pay each month for your mobile bill?
— Martin Lewis (@MartinSLewis) January 13, 2022
"If part of that is repaying a handset, fair enough. If it’s because you roam a lot, then fair enough”, Mr Lewis also said. "Maybe if you’ve got poor credit and you have to be on pre-pay, but that shouldn’t be too much more expensive."
He also recommended people switching their SIM card to a cheaper deal in order to bring down the price of their bill. Smaller providers use the same signal as larger ones, but often at lower prices.
Anyone who wishes to swap their SIM card but also keep their current mobile number can text PAC for free to 65075.