Price Rise on BB During Initial 12 months

[Gofer]

More of a rant than a question.
Joined NOW BB in March paying £22 a month on a 12 month contract.
I switched after other suppliers had announced their annual rate of inflation+ hikes.

After 3 months NOW increases my monthly payments to £25.50. 
Apparently first rise for a few years so, though annoyed, I let it go.

Looked at website today and they're advertising my BB package for £21 a month on a 12 month contract.
So, it appears new customers are being offered a great deal which is good for them but what's to stop NOW upping their price after 3 months.

Surely legislation is required to stop mid contract price hikes - not apparently related to the "sanctioned" rises and then lowering intro prices for new customers.

[RoyB]

@Gofer 

Because this price increase isn’t contractual, Now Broadband have to let you go, penalty free, if you ask to.

I suggest you call them, state you beef, and ask nicely for the £21 rate.

Numbers are below. Ask for ‘Retentions’, as they have the most flexibility here, 

Try 0330 041 2518, 0330 041 2462 or 0330 332 3050, and maybe 0800 759 1213