Dialing the number from the mobile has resulted in the same issue, this suggests there is a problem with the other number.
As this issue falls outside of MyRepublic's network, we can't troubleshoot any further. However, we suggest getting in touch with the person who owns the number you can't call and let them know. They may need to check with their phone network provider to troubleshoot the issue.
If you require further information on this issue, you can contact us here.