Problems switching to plusnet - phone cutoff

[#1]

Am hoping I might be able to get some advice here.  My mum, in her eighties and living alone, is in the process of switching to plusnet and yesterday her phone line went dead.  The order update information says her phone will be transferred late next week.  She spent sometime yesterday contacting plusnet on her mobile (payg) but just got the check your sockets runaround.  We've raised a ticket but looks like it takes 27 hours to get a response, and the help desk won't speak to me as I'm not the customer.
Does anyone have any suggestions or is she bound to be without her landline for the whole week, she's quite scared at the prospect of this
Thanks

[#2]

If the transfer is not until next week then it's still the original provider that is responsible for the line.
If you are transferring from BT then it's only a billing change and no physical work is done to the line.

[#3]

Her current phone supplier is southern electric - therefore not sure whether  the actual provider is BT or someone else (a quick google didn't clarify)
Nothing's changed in her flat and she has a wired phone plugged in - so am assuming the dead line has been triggered by the switch
She tried to ring southern electric on her mobile but had problems getting through - I think she was too tired at the time as  it took her an hour to have a conversation with Plusnet after 20 minute waits and getting cutoff several times
I'll suggest she tries them on her mobile  if I can find a non 0800 number for them

[#4]

Hi,
Sorry to hear about the problems you are having. The ownership has now yet transferred so therefore itsme is correct. I did a check for a phone number and could only find 0800 294 4721 for southern electric's phone faults team.
Twills.
Plusnet Faults.

[#5]

If that 0800 number is the only option you might find the suggestion to use the 0800 Buster service mentioned here of interest.