Asterisk ARI call from external to external

I want to make a call using Asterisk 13 ARI from my mobile number to another mobile number. I have tried different calls but all return “Allocation failed” response:

endpoint:my_mobile_number,extension:other_mobile_number,context:from-trunk endpoint:SIP/my_mobile_number,extension:other_mobile_number,context:from-trunk endpoint:SIP/my_mobile_number,extension:other_mobile_number,context:from-external endpoint:my_mobile_number,extension:other_mobile_number,context:from-external etc.

How can I initiate a call from my mobile phone to another mobile phone using ARI?