Bharat Sanchar Nigam [BSNL] — landline number [protected]

I am your customer last 20/25 years. We do not hear anything through telephone. I made complaint under docket no.[protected]. Your service man sri kanai chandra naskar came to our house and told that the instrument is faulty and you purchase a new instrument and fit it.
I submit whether i have lawfully entitled to replace your instrument with my instrument. Whether i am paying regularly your rental but your telephone will be out of order.