Generally, the only way to guarantee you’re not penalised for cancelling a contract is to cancel within the cooling-off period.
Before 23 January 2014, there were no rules in place that allowed you to cancel because of price hikes during your contract.
If you cancel before the minimum contract term is up and your contract started before 23 January 2014, you’ll have to pay an early termination fee. These can be very high.
Rules set by the regulator Ofcom mean that customers can leave mobile, landline or broadband contracts penalty-free if a provider ups prices mid-term - if for example there's a rise that's bigger than the RPI rate.
You can cancel your contract and switch to any other provider, as long as you do so within 30 days of receiving your price-hike letter.
But if your landline provider has warned you about rises in their terms and conditions and they are in line with RPI, you won’t be able to leave if you’re still locked into a contract. If you do want to leave, you'll have to pay an exit fee.
If you’re outside the minimum term of your contract then you’ll be allowed to leave without paying. You should check with your provider about how much notice you need to give to do this.
Your landline provider may be able to hike the price of your fixed contract by the rate of the Retail Price Index (RPI).