Wont accept calls after port

[#1]

Hi

I changed my phone from virgin media (o2 carrier I beleive?) To plusnet it appears that my phone will now accept calls from some mobiles but not others. Specifically it won't accept calls from my other half's phone she is virgin media still and just gets a dull tone and then it hangs up on her when she trys to dial me... any ideas.

The phone has been on and off several times and I have tried resting the network data settings but it's still the same

[#2]

Welcome to the Forum,

Have you entered the PN APN settings for your phone see below scroll down to 

 What are the APN settings for my phone?

 https://www.plus.net/help/mobile/mobile-phone-and-voicemail-settings/

[#3]

Hi Thanks for the reply.
I've tried it its not worked no change at all. Spoke to tech help who suggested the same. So did it again and it still didn't work. Have tried aeroplane mode for 20 mins no change
Reset the network no change
Turned data roaming off and on again and have turned the phone off and on several times
So still won't accept the calls
Any ideas greatly received