Broadband and mobile companies such as BT, O2 and Vodafone use the rate of inflation to set its price increases.
Broadband and mobile customers could see prices rise by 10 per cent by April 2022 if inflation hits 6pc.
Research from Choose revealed that 87pc of broadband and mobile customers did not know that prices may increase by as much as 10pc and 46pc did not know that prices would be rising at all.
A third of those surveyed were unaware that bills could increase during a contract.
One in four said they would find it financially difficult if bills increased by 10pc, while 11pc said they wouldn’t be able to afford a 10pc rise in their bills at all.
Ofcom reported that 65pc of broadband customers and 89pc of mobile customers are still in-contract, with no way for millions of customers to avoid paying higher bills.
Choose MD Lyndsey Burton said: “Broadband contracts are usually between 12 and 24 months in length, with many customers signing up to 18-month deals.
“Surely it is fair and reasonable to expect providers to fix their prices completely during the contract period to ensure customers know where they stand financially until the contract runs out.
“Ofcom either needs to ban mid-contract price hikes completely or, at the very least, they must set a cap that more fairly distributes inflationary costs.”