How to tell if a 'phone has switched from BT to a different supplier?

A question about : How to tell if a 'phone has switched from BT to a different supplier?

I have two pensioner friends who are fed up with BT's price rises and fiddles with BT Privacy/Caller Display, 1571 and free evening & weekend calls ... all tying them into regular 12 month contracts multiple times each year.

Both use BT for landline and both use PlusNet with a legacy tariff for broadband as they live in a small village.

One has struck an unbelievable deal with PlusNet with 12 months unlimited broadband in a high cost area for Ј3.00/month plus line rental in advance.

I tried for such a deal with the other person who lives 10 metres across the road in the same village and has the same broadband for 7 years. No luck, Ј8 unlimited broadband offered on a 12 month contract haggled down from Ј10 unlimited broadband for a 24 month contract + line rental in advance. So we gave up with BT & PlusNet and moved her to the Post Office for telephone & broadband.

My question is, how can they tell for certain that their telephone line rental has been switched from BT to PlusNet or the Post Office? They both switch sometime on Monday 16th February. Neither of them wish to give BT any more money for calls!

I have searched and searched and cannot find an answer.

I'm hoping there is a free and quick way by dialling a special code/number to check if BT is no longer providing the line.

I have no worries about who supplies the broadband ... that is easy!

Thanks in advance for help.

Best answers:

• Dial 1571 and the message you hear should be slightly different from the BT one. It definitely is for Plusnet but not sure for certain for the Post Office
• BT customer service is (I think) 150, so dial 150, call answered by BT, still a BT line, answered by someone else or number not recognised presumably changeover has taken place
• Thanks for the replies. I'd thought about 150 and I'll certainly give it a try.
  One of them uses 1571, so I'll give that a try too.
  I also realised today that neither of them have caller display with BT as they no longer wished to be trapped into a contract to get it "free" and they didn't want to pay for it. However, both have opted for free caller display. Usually 99p with PlusNet but my friend negotiated it free for 12 months. The Post Office provide caller display for free at the moment. So I guess I could also keep calling their lines from my mobile 'phone until it finally displays and then we'll know for certain their line rental is now with their new supplier.
  I know it only happens on occasion but greater clarity of who is currently providing a line would be very welcome.
• The Post Office service is now from Talk Talk,
• A Plusnet service still comes over the BT network, as they're owned by BT and offer only a non-LLU service.
• Teddysmum,
  Yes TalkTalk provide the broadband and calls infrastructure but not the support, that is provided by Capita. Also the Post Office offer more than TalkTalk in market 1 exchanges.
  I'm with TalkTalk on LLU as they have a presence in our local exchange and when I dial 150 it goes through to TalkTalk customer services of some sort, but it is clearly announced. I'm happy with TalkTalk and if I have a problem I pursue it through their members forum instead of over the 'phone as the support is far superior.
  My mother's exchange is in a small rural village with only BT having a presence (Market 1) When she switches, I will try 150 and see who answers if anyone and feed back to this thread. I have several friends in similar rural locations in Norfolk/Suffolk where there is little choice for cheaper broadband than most of the population can get as standard, and they are very happy with the Post Office. OK the Post Office have an 8 Mbps cap on their broadband but as the exchanges in question aren't enabled for ADSL2+, it makes no difference.
  I'll just be glad when my mother is rid of BT.
• Both switches have now happened and both parties had a mystery