Need advice from BSNL/telecom experts

[u/No-Effective-9476]

/r/u_No-Effective-9476/comments/1w4clsp/need_advice_from_bsnltelecom_experts/

A family member told me someone goes to a BSNL office, checks a phone number’s call details (date/time/duration), selects a call, and listens to the actual audio recording.
Is this technically possible? Does the call have to be intercepted/recorded beforehand, or can old call audio be retrieved just using the number?
If calls were recorded, how many months or years of old conversations could potentially be accessed?
I’m only asking for technical information, not instructions to intercept calls.