Call outbound issue

I have this scenario where I have 2  sim cards attached to TG1600. Yeastar S300 with PSTN provider attached and with fxs where the phone is attached.

Now the issue is when I outbound call through sim card it will go through, however when I try to test call using the sim 1 and call the other sim 2 attached to TG1600 it won't. 

It's weird that I can all outside my premise but not the other sim inside the TG1600.

Please help.


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