I don't think Talk Talk guarantee the price for the term of the contract like Plusnet do.
Off the top of my head they state there will be an annual increase of up to CPI+3.9% but have to give you the option of leaving penalty free within 30 days of notifying you of the increase.
Not true. If they make an increase which is *not* in your contract, you can leave penalty-free. But if you signed up to CPI+3.9%, they will keep you to it.
See: https://www.plus.net/help/legal/cpi-plus-guide/
Can I cancel my contract because of these changes?
If we're only putting up the price of broadband, line rental, call plans, call charges and BT Sport in line with the CPI plus 3.9% and you choose to cancel because of that, you'll still need to pay any early termination charges if you're still within your minimum term. This is because the amount we can increase your price by is fixed to any increase in CPI plus 3.9% and we'll have made the price increase clear when you signed up and you'll have agreed to it in our terms and conditions.
If we put up our prices for any other reason though, you might be able to end your contract early without paying any charge.
TalkTalk did something similar to Plusnet a while ago they upped the price but gave the option to leave (as said in the other post) and this is the rest of the message is below -
Each April, we’ll adjust the monthly amount you pay for your broadband and increase by the Consumer Price Index (CPI) rate of inflation plus 3.7% (which is lower than Vodafone, BT, EE and Plusnet’s current price rise commitments).
The CPI rate that we use is announced in January each year and we will adjust your bill by this amount, plus an additional 3.7%. This change will only apply to our broadband packages (some exemptions apply).
For example, the CPI rate announced in January 2021 was 0.6%, so all relevant customers’ monthly plan prices from April of the same year would see an increase of 4.3%. So, if you normally pay £25 for your broadband service, your new monthly charge would be £26.08.
If the CPI figure is negative in the relevant year we will only increase the charges by 3.7%.
These changes are being made due to increased running costs and further investment in the network. They will allow us to continue to offer resilient, totally unlimited usage as standard. That investment also means we can bring faster speeds to customers, including full fibre, to help meet increasing data demands.