Question Call waiting not working

[mArIuS%]

I'm having a problem with call waiting, people ar calling me and they get the busy tone eve if call waiting option is enabled, it's just me having this problem or it's common, is there a way to fix it? I am pretty disappointed of this phone, eve the stables releases of firmwares are buggy and realme doesn't even borrow to give a feedback to E-mail or bug reports.
Waiting call is enabled on phone and network provider, phone is with Android 11, RMX3081_11_A44 Europe.

 

[StratOS_HTC]

Well this is based on ROM settings and location settings. If provider can enable 2 lines there is no problem as you set and it's enabled.
Mine is working on GDPR rom.
Check the Engineer settings ?

 

[mArIuS%]

Refuse to work, i did a phone reset and didn't help, if I insert the Sim-card in other phone call waiting is working. Why should I do on engineer mode?