MTNL Delhi — Digital Telephone instrument not displaying any digits and other informations

Address:

South Delhi, Delhi

My digital Telephne set installed by MTNL does not show digits of date and time and dialled digits. Inspite of several reminders It has not been replaced so far.
Line man telephone mechanic says that the instuuments are out of stock from the last several months. Kindly help to replace the set or rectify the defects in the existing set.
V L Khanna Ph. 26241136 Ad. 6-B DDA Flats Masjid Moth Phase 1 New Delhi 110048