We've had a look at your account but couldn't spot any issues which could have an effect on your inbound calls.
Our only thought which could have an effect on this is you may haveblocked our 'Another Number Incoming Call' contact, because the app utilises this contact for inbound calls, you must have it unblocked.
Please do the following:
1. Go to iPhone Settings
2. Select Phone
3. Select Blocked Contacts
4. Unblock the entry that has 'Another Number Incoming Call' (+443300930099).
Then please try a new incoming call, let us know how you get along.