Airtel — not connecting any calls to a bsnl landline

Address:

Bangalore, Karnataka, 560069

I am also facing this issue from past 20 days. When i call a landline no within a karnataka circle (In karnataka only from one district to another district) a voice telling like 'this call cannot be connected'..., i called customer care and those people are telling like, from our side there is no issue..! I changed the sim card between 3 different mobile handset, but issue remained same, airtel peoples also unable to find any issues with my no..?