I already posted this at the end of another thread, but I thought it would be useful to re-post with a link to the solution. I have an Android phone with 400+ contacts, and all numbers are in the international E.164 format. Examples: Domestic US/Canada (zone 1): +1 205 555 1212 International (other zones): +61 456 5555 1212 This format works just fine with my Mobile provider (Verizon). I have a SIP phone (CSipSimple) that will successfully start SIP calls with E.164 numbers, and is integrated into my Android contacts list for alternative dialing. I wanted to be able to use the contact phone numbers directly. The solution is in the E.164 setup in 3CX. See this post for details.