Can't call certain numbers??

I’ve been trying to call my brother, and a cousin of mine. But when I dial their number -- NOT using stored contacts, I keep getting a 6UC2 message saying that the call cannot be completed.

I’ve tried multiple times the last couple of days and keep getting the same message. But I can call other numbers, both manually dialled and from contact list and the calls go through just fine.

I ended up using  my wife’s phone, which is also through Koodo, and both numbers work just fine and I can talk to both my cousin and brother. Any ideas of what the problem is?

There’s no problem with my SIM card. I’ve restarted  my phone several times. My bill is up to date.  I just can’t get these two calls to work on my phone at all!