Numbers may be stored in your contacts with a leading + (plus) sign.
The + character is not currently supported by our network.
You can add Number Rewriting Rules to Real Softphone, that will remove the + sign, allowing you to dial out without changing your contact numbers.
Click Settings -> Preferences -> Number Rewriting.
You should have these two rules added, in this order:
- Starts with +1, replace with 1
- Starts with +, replace with 011