microphone w850i?

i changed the casing on my 850i everything works but no one can hear me talk on closer inspection there was no micro phone fitted in the new casing as i had thrown away the old casing i could not retrieve the mic. i bought a new mic but it does not make contact with the motherboard i tried another mic but that does not work either are there contacts from the motherboard to the mic or a spring in the casing to put pressure on the mic any help please.