Can T-Mobile/EE change my tariff one day out of contract?

HelenBishop

I currently am on a very good grandfathered plan on T-Mobile; Unlimited Texts, Unlimited Calls, Unlimited Data, Unlimited Tethering at a good price, the only thing is it's 3G but very fast and efficient.
My contract is finished and on rollback.
I have seen Three do the same offer on 4G but with 2GB Tethering.
I don't mind the capped Tethering as I don't use that much anyway but when I read about it I saw a bunch of articles and forum threads saying it used to be unlimited but then they changed it for everyone out of contract.
I know grandfathered plans are rare and getting rarer and plan on keeping a good plan for as long as I can (I don't really care about changing phones), as my mother bought a phone when phones were new and they were encouraging everybody to buy one and the offer was buy this phone for £600 and get Unlimited Calls & Texts for life. She still has it.
I would like to do the same but I know unlimited plans are rare and getting rarer so I do not want one day for Three to decide that they do not want to do unlimited plans anymore and then just change my tariff like they did with the tethering people.
While at my local mall were there is a EE/T-Mobile and Three store 15 seconds from each other I gave my concerns to an employee at the Three Store and they said that all providers including EE/T-Mobile can in fact do that.
Not putting my trust in any of those people I went to EE/T-Mobile were they said it wasn't true they would not be able to one day change my plan, if I've got it I've got it. I also don't trust that specific sales representative as he had lied to me in the past.
So far I have been out of contract with T-Mobile for 3 months and everything has been fine, my 3G is fine and is not something worth going into a risky contract for.

So which one is correct?

Collabora

you were on contract on a grandfathered plan, this ended and EE changed your plan. yes they can do that as you are no longer in contract so the grandfathered plan no longer is available. you also need to give EE 30 days notice of leaving.

Once you have signed to a plan then they cannot change this unless they give you at least 14 days notice, so three could not decide in 1 day to change a plan and do this without letting you know

grumbler

They can change your tariff whenever they want. They just have to give you a notice, I guess one month in advance.

ZhugeEX

Networks can do whatever they want when you're out of contract.

They can also do whatever they want when you're in contract. The only difference being that when you're in contract you'll be able to cancel at no cost to yourself.

The Three example is quite extreme and something that no network has done before and probably won't do again. But as you can see, it does happen.