I am using Zoiper 3.5.3 on iPhone 6 and I am unable to make international calls when on my cellular network. I get the error 404 "Not found". When logged onto my wifi network it works fine. I've tried dialling using the international + prefix as well as 00.
Can anyone give me a tip to which setting may be wrong in my client? There are no limitations on my cellular network for data usage of any kind...
Thanking you all in advance, kind regards