I have WLL connection sine last two years. The battery back up is not at all working,means the instrument won't function without external power supply. When contacted the Customer care demands me to pay for a replacement battery. This is absurd and shocking as the instrument is the property of Tata Indicom, they need to maintain and replace it unless the instrument is damaged by the user just like any other telecom e.g. BSNL.
The customer care just put you on hold for long time and comes out with negligent answer, may be my worst experience.