Airtel — volte services never activated on my sim

Address:

Hyderabad, Andhra Pradesh, 500055

Date of the incident - 18th april
Client number [protected]
Full description - volte services never work

Despite of thousand calls and thousand requests no one from airtel took the accountability or responsibility to assist on getting my concern resolved. Never expected such pathetic services. I have sent multiple emails to [protected]@in. Airtel.com and i have spoken to multiple supervisors, none could answer my question. Now they are asking me to pay the bill, when i asked why should i pay the full amount when they failed to provide me full services, no answer from anyone.
They said it's a problem with my phone - i changed phones multiple times and checked, but i could never enable volte
They said it's a problem with the sim card - i ve' been to the store and replaced the sim card either, but it never worked.
They said please check the settings and put the sim in sim1 - i did everything and infact i tried with multiple phones as i suggested above, but no luck.

Someone please help me, i seriously wish to take this issue legally, as a customer i pay money and i expect all promised services.

Muralikrishna m