@TPint 

What is the current network diagram？ 

Does Archer D50 wrok as a bridge to synchronize the DSL connection? 

When you uncheck the wireless network, did you press save and reboot to apply the settings?

Meanwhile, is there anybody else who pressed the wifi button to turn it on? Theoretically the wifi feature won't turn it on automatically.

And when and where did you buy this router? 

Best regards. 

I bought my modem/router on amazon, and yes, i've tried averything.

My Archer D50 is setted on bridge mode, its only function is to give the dsl connection to my router. (I've deleted all the connections and created a new one in Bridge Mode)

Yes, i've pressed save and rebooted after i've unchecked the 2.4 Ghz, and nobody has pressed that button other than me.

My network diagram is simple: TP-Link in bridge mode attached to another router (pcwrt)

https://www.pcwrt.com/

I had a d-link modem/router before the TP-Link, and never had this problem.

The things works great, but this problem is really annoying, help me please.

@TPint 

First, cause the Archer D50 works in bridge mode to give the DSL connection to your router, you do not have to disable the wireless function; The reason is that the Archer D50 is bridge mode by default, even though it still broadcasts wireless network, there will be no internet from it; 

Otherwise, you can contact the tech support with the proof of purchase and serial number to verify whether this device is still under warranty. 

https://www.tp-link.com/support/contact-technical-support/#E-mail-Support

Best regards.