Communication failure

Climbing from 3500 to FL 70, Lose Contact with Tower

4 turns, word for word from the oral. Read the pilot lines out loud.

The exchange

4 turns in order
01
You, the pilot

Mumbai Approach IFLY 160 Heavy, negative contact with Delhi Tower, climbing 3500 for FL 70

02
ATC

IFLY 160 Mumbai Approach, maintain this frequency, climb as cleared, reciprocal traffic INDAIR 430 Heavy descending to FL 70, estimate to cross at 37 DME

03
You, the pilot

Climbing as cleared, reciprocal traffic INDAIR 430 Heavy descending to FL 70, estimate to cross at 37 DME IFLY 160

04
You, the pilot

Mumbai Approach IFLY 160, DME 37, INDAIR 430 has reported DME 26, request climb FL 330