Hi @ Donna Stallings,
What is the make and model number of the phone?
If possible try using the earphones with microphone attachment or try using the phone in "loudspeaker mode" when making or receiving a call and check if you can be heard OK.
If so, there may be a problem with the phone's internal microphone or perhaps the voice inlet hole at the bottom of the phone is blocked with lint etc.
Try using a vacuum cleaner to see if it clears any obstruction from the voice inlet hole.
Do not use a pin or probe to try and clear it as you may damage the microphone which is located directly behind it.
If still no good, the phone will have to be opened and further diagnosed as to what is wrong