You may need to speak with your network provider to ensure no barring is in place and both of you make sure that neither of you have inadvertently added your numbers to call blocking in the phone.
Launch your phone app and press the 3 dots in the top right hand corner and check out the settings there.
As a process of elimination to rule out the phone try your sim card in another phone if you can @Britboy1950
Your partner will also have to check with their provider to ensure there are no issues and to check their own phone settings too.
Current Phone ~
Samsung Note 20 Ultra 5G SM-9820 _256Gb SnapDragon 865+
Samsung One Ui 2.5/ Android 10.
@Britboy1950: Can you try opening the Phone app > Tap the 3 dots in the top right > Settings > Supplementary Services > Call Barring > Voice Calls, and make sure that all Outgoing Call options here are toggled off?