How do I know when change from FTTC to FTTP is complete?

[#1]

I have just been upgraded to FTTP, but my old copper phone cable from the BT pole is still in place and has been joined by a fibre cable.  I intend to keep my old phone number and use a voip service from A&A or Voipfone, but I understand that I must not attempt to contract this service until the migration is complete and the phone number is in limbo or I may inadvertently terminate my new  broadband service.

My question is, how do I know when the migration is complete?  My broadband service is working on the new fibre connection, and my old phone service provided on the copper BT cable is still working 2 days after the fibre installation - there is still a dial tone, and I can successfully dial my number from my mobile! 

Can I contract for my voip service now, or do I need to wait until the old phone service stops working??|

[#2]

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@davec13 wrote:

My question is, how do I know when the migration is complete?  My broadband service is working on the new fibre connection, and my old phone service provided on the copper BT cable is still working 2 days after the fibre installation - there is still a dial tone, and I can successfully dial my number from my mobile! 

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That sounds surprising, mine ended the same afternoon the ONT was commissioned - perhaps they have forgotten you?

I'd suggest it is complete when you can no longer dial your landline phone. Or when 17070 indicates a different number on your landline to yours. My phone line continued 'working' electrically for about a month after that.

[#3]

Thanks @pvmb for your very speedy reply.  I didn't know about the 17070 test service and I have just tried it - still my old number!

I did wonder if part of the problem is that the fibre installation was done in 2 separate visits. The ONT and fibe connection to the external junction box was installed last Friday, and the new cable from the pole to the junction box was installed this Monday (by a different engineer).