Campaigners seek a ban on 070 numbers which cost over 50p a minute to speak to sick loved ones.
OFCOM has launched a probe into NHS hospitals that force loved ones to ring premium-rate lines to speak to patients.
Campaigners want a ban on 070 numbers, which cost 50p a minute or more and begin with a long recorded message, which racks up the bill.
Private firm Hospedia, which runs TVs and bedside phones in 150 hospitals, made £21.2million in 2016. It pledged to phase out the lines but has not.
Ofcom says 070 numbers can be confused with mobiles and warns there is “evidence of scams”.
“Given the rising cost of calling these service numbers, Ofcom is launching a Call Cost Review, to ensure that prices are transparent and fair to consumers,” the regulator said.