Default d838 with speaker problem

good morning
I bought this amazing devise but I face a problem
that the device stuck on ( external ) speaker only
i can't make any call by using internal speaker .
after some time it will work normally for 2 or 3 days
i tried to make software but i couldn't as this is the first Lg for me

Restart didn't do any think.

now when i face this problem i use earphone

any help?