The practice of using a telephone system to manipulate user into disclosing confidential information is called?

Vishing

Explanation:

Vishing - it is refer to that fraud tactics that use cellular phone, through which user get ready to enter their personal information or financial details. It is conducted through phone call.

In this caller call to the unknown person and pretending himself or herself from very reputed organisation. And once caller get trust of the receiver, demand personal information which can be used for stealing the financial details.