Looking for a way to disable/eliminate wifi tethering (sharing of internet).

Currently here in the Philippines, re-selling of internet is now being made as a home business, however, wifi tethering makes our profit low to almost none.

See image below for your reference on how customer take advantage of tethering.

This is the only problem we encounter using tp link for this type of business and hopefully we'll have a solution to this and if there's a way to eliminate mobile tethering please share it with us.