08456021111

Sounds like it was a scam call where this text service number has been spoofed and pressing a button could have been expensive. The introduction when you pick up will always tell you the originating mobile number.  If no originating number - hang up. If you are told the originating number check that number out before risking pressing numbers.
Tip: If this number calls again and you are not sure, stand next to your landline with your mobile and send a text to your landline. If the computer announces that you have 2 texts and one is from your mobile, you can safely listen to both. No charge to answer these calls.
Be aware that these text to landline audio services will not filter out scam text messages and if the message is a scam attempt, the originating text number will be the scam number to report.

I was called from 08450021111 just after 9.30 am on 27/10/2020. Calls from unknown numbers that cannot be traced are always troubling but can be distressing when family members are undergoing medical treatment or waiting for test rests. A menace...!

08450021111? Probably a wrong number. Someone wasn't taking care when they punched in the phone number. Easily done.

But I'm not on BT Landline, a different provider beginning with V.
I wonder if this has been switched in some way so I think it's BT?

This BT Openreach service translates a text message into audio and relays it to non text enabled landline phones. Most phone providers including Vodaphone and Virgin use this service.  Whatever phone provider is used for a landline, most send their signal along the Openreach lines. Try sending yourself a text message to your landline to find out how it works. No cost to answer and listen to your text. Don't use emojis as this will cause the ancient BT computer a few problems ;-{

Jean, Your order is ready for collection

It may be a scam because scammers use this service to dupe people into ringing back on premium rate numbers. They leave a message such as, "Hello mum, please ring me back urgently on........."

If the person rings this number they will be charged the earth for the call. Be careful!

The cost to call this number to retrieve a text message relayed to a landline is 5p per minute plus your network connection charge. Be aware that these messages get deleted after 24 hour. This is a business rate charge not premium rate. Premium rate numbers usually start '09'.  But it is possible to retrieve a text message without a cost. The method for doing this is exactly the same as checking whether or not the call from this relay service number was genuine or spoofed. Just read back a few posts or even a few pages.
If you get a scam text or message relayed via this number, this service will ALWAYS tell you the originating number. That number and details of the scam attempt should be advised directly onto the police fraud database.
Type 'action fraud' into your search engine, click on the 'police.uk' site, click on the 'reporting' icon/button, from the dropdown box select the phishing reporting section, scroll down past the scam email info to start this report. No registration is required. It is important that all scam attempts get reported so the police can get an understanding of the extent of criminal activity.

Bit of an exaggeration, mate, but wondering why you replying to a post from 248 pages & 12 years ago?

3 times today 24/11/20 I did not answer and my answer phone did not come for who ever it is to leave a message.

Just had a call 23.55hrs from this number

We have been having multiple calls from this number. Very annoying

Frequent calls after 9pm stating I have a text message press 1 2 or 3. I just hang up. They called twice in 5 minutes, last call 9.39pm. I just hang up, nuisance calls.

Shortly after agreeing to take part in a medical study (on my landline), I received a call from BT SMS text service confirming my phone appointment. It was so garbled I didn’t realise that’s what it was, as I hadn’t given them my mobile number.

just adding my unsolicited call to your list. My landline rang periodically. I never bothered to answer: any callers of relevance would have my mobile number. The fact that this 'caller' persisted so metronomically hints at an electronic scam, methinks. Is there any way of discharging 4,000,000 volts down the line to the 'caller'?

Probably too late now to check that call from this number but it is a text to landline audio service operated by BT/Openreach on behalf of most phone providers. Someone sent a text to your landline.  Look back over the past 4 or 5 pages to find out more about this service and how to avoid the scammers who have been known to misuse this service -  just in case it calls again.

How dare they call me on Christmas Day