Not sure why this has been marked solved. I've had exactly the same thing since yesterday and it's only doing it when I call my missus phone, which is the one I call the most. 100% correct number as it's been in my phone for years and is 1 digit different to my own. She is on EE, I'm on VM Mobile if it's related.
My phone is a Samsung S9, but I've also swapped my Sim into an iPhone 7 and get the same thing.
Looking on EE's community forums, it has been an issue for users before and was resolved in the same day... VM need to look into this or approach EE for the solution.
I do not call many number, but from the handful I do call, there is only one that's not connecting, my wife's, who is on with EE. Still doing it today. Number is 100% correct. She dials me, it's fine. I return her call, it doesn't exist. SMS works fine.
Thought I'd give it some time, incase it was a blip that may correct itself, but it hasn't.
This exact thing happens to me and for a week now calling my mum which is a valid number says incorrect number I have called Virgin Mobile over eight times and on four of these occasions the number has gone dead and nobody has called me back they are looking into a complaint of mine but nobody has rang me back and it’s still continuing!!
I have tried a new Sim card I have tried my Sim in a different phone there is a fault and Virgin are doing nothing to solve this my mum is the person I called the most and it should not be saying an incorrect number