how do i know my phone is locked to which network?

Dear All,

I have Samsung Phones from UK and it is Network locked.Is there any way to check which network my phone is locked? Bcoz i need to buy unlocking code.

Here is the imei :
356650095470854 ( SAM- A520F 2017)
358138097058222 ( SAM - G950F )

Your quick reply will be highly appreciated!

Regards,