can anyone tell me what's the use of wifi calking and how can it be used?also tell me how can we use WhatsApp calling?

everyone knows now pros and conssome points to be noted-1. no 3 finger screenshot2. can't take selfies using fingerprint3. front camera isn't upto the mark as expected.4. network issue5. no applock6. WhatsApp video call issue7.no recorder in call8. n...