When i call someone i can hear them they cannot hear me

There are two things that can cause such a problem to happen. Below is each possibility carefully examined and given proper solution.
First of all, it is possible that you have your phone on discreet mode also called the muted mic mode on some phones. Some phones come with a function that allows you to disable the mic before you make the call. It is important that you check properly to make sure that the mic is not disabled because this prevents your voice from being transmitted and acts as if their is no mic to transmit your voice to the other party involved in the call. If the mute function has been enabled, you have to disable and this should solve the problem.
On the other hand and most likely to be occurring, the possibility that the mic of your phone is damaged is very high and would require a replacement. This is the only way to solve a problem with a broken mic. It is not very advisable to fix it even if it can be fixed. This is because patched up mics do not last long before they go broke again. If you are convinced that you mic is faulty, you have to send the phone for repairs or replacement as sorting this out requires real expertise and care which cannot be provided by one who has little or no knowledge about this thing.
Hope this was helpful?

Its the problem with your phone's microphone. Try using a hands free device to make the calls. If both party can hear each other, then it confirms the micorphone problem.
Take your phone to a nearby local repairer to get the microphone fixed.
But in the mean time, enjoy your calls with the use of the hands free device to enable both party hearing each other.

Hope that was helpful?
Take care.

I will start to search for the culprit (SIM or phone).
Try to change the SIM card in your phone. Just take out your SIM and insert another one, have another one borrowed.
If the problem is gone than probably it is the SIM (dirty contacts, chip malfunctioning, bad network access). Call your mobile company and ask for a replacement.
If the other SIM has the same problem then it is probably the phone. Try to turn off the device or, better, try to apply a soft reset.
If the reset does not solve the problem contact device assistance and explain the defect and the test you have already run.
If you are using a handfree set try another one.