Echo in voice to the caller while receiver with headphone hving wire replace
It seems that somehow your "replacement of wire" has caused a situation where the received signal is partly being sent back or being coupled onto your microphone circuit. 

Possibly both receiver and microphone wires are running adjacent without any shielding. At the least you should use twisted pair for these wires. 

If you pay attention to this aspect, you should be able to resolve your problem.