Giffgaff numbers coming up as invalid

[Chrissi66]

My Oh and I are both on EE. My daughter and SIL are with giffgaff. We are unable to ring or text either of them. Texts are undelivered and when we call it says the number is invalid. We can receive incoming texts and calls from them.

We are the on,y ones they are aware of have a problem and we are their only contacts, as far as know, on EE.

we are able to contact them on our phones via WhatsApp.

We have tried all the usual tricks of restarting phones, deleting, reinstating contacts, adding the international code. My daughter has replaced her sim to no effect. The only ‘progress’ using the international prefix is that the message has changed and now simply constantly says that ‘the network is busy, try later’. 

What do we try now?

Thanks

[bristolian]

Are your daughter & SIL using Giffgaff-issued numbers? And if so, did they get those numbers recently? Don't post the whole number, but what's the first-5 digits?

Or are they using ported-in numbers?

Have you or your Oh been been able to call/text these numbers previously?

[Chrissi66]

No idea re porting, they’ve both been on giffgaff for years and we could ring and text them in the past. I can’t quite remember when the problem started as I tend to chat on my daughter on messenger rather than calls or text. 
I think it’s fairly recent, but definitely been going on some months. At first, I just thought it was a temporary issue so didn’t really pay much attention and it was OH who had the problem first (or discovered the issue as he doesn’t use messenger and at that point WhatsApp). 

there numbers are 07523 and 07892

[bristolian]

Those numbers are both O2-issued thus a porting issue can be ruled out. Equally if they've been on GG "for years", then an issue with newly-issued prefixes doesn't apply.

That's the two most common reasons for problems calling individual numbers. WhatsApp & other internet-apps route all their traffic over the internet not via the mobile network, thus that observation merely proves your phones have working internet connections.

I would suggest contacting CS and report the inability to call individual numbers that you know are valid. If you can quote  handful of examples of failed calls over a 2-3 day period, that would be useful. They should follow an escalation process culminating in an individual fault ticket being raised into networks teams, for those specific calls to be checked against call traces - this should give an indication of the cause of the issue.