Other person can't here me speak

newer blackberries turn speaker phone on by when your in a call pressing the blackberry button next to the control pad to bring up options and then scrolling to find speaker phone on this may work

To unlock the Blackberry Curve 8300 ,Buy the unlock code for Blackberry 8300 from the site Mobile-unlocker.com and unlock it.You can enter the unlock code following the instructions below:

Warning : Do not enter any wrong unlock codes on your Blackberry 8300 Curve mobile phones. If you enter over a certain amount of wrong unlock codes on your Blackberry 8300 Curve mobile phone, your phone may get hard locked and sometimes become unusable.
1 - Switch on your Blackberry 8300 Curve without any Sim card.
2 - Go to Settings.
3 - Go to Options.
4 - Select Advanced Options.
5 - Select SIM Card.
6 - Hold the ALT Key while typing in MEPE or MEPD or MEPPE or MEPPD ( not case sensitive ) ( you will not see text appear on screen while typing ).
7 - You will then be presented with a prompt "Enter Network MEP Code". Type in the Unlock Code and press in the track wheel / jog dial to confirm,
8 - Your Blackberry 8300 Curve will now be unlocked.

had same problem.
1) connect earphones and try a test call. If it sounds ok with h/phones then
2) record yourself / some music and see if it plays back ok. If it does then it's not the speaker or microphone. I found that this test miraculously cured the prob.
If it doesn't then take it back to supplier.

then you should take the phone and have the speaker replaced or the pcb main board looked at.

How long have you had the phone? Use the appropriate means through your carrier to have the phone either warranty replaced or serviced. Depending on your carrier their customer service number should be on your bill. If you need further assistance let me know. Thank you,
Lee

This will typically happen when you need to clean your trackwheel.

I've done this, but it's a little scary - it looks pretty easy to break your trackwheel..
http://www.blackberryforums.com/general-8300-series-discussion-curve/108122-how-clean-your-8300-blackberry-trackball-pic-guide.html

sound as in you can not hear the person speaker or the phone ringing on your end....if these are the problems maybe the BT headset is faulty

you will need to take this up with your carrier it does sound strange...maybe you could try entering the area code before dialing the cell number.

Your speaker could be going out.  When making a call press the $ button to activate the speaker.  See if that function works.
Adjust the volume with the volume control on the right  side of the as needed.

Try using the voice dialing feature. I had the same problem until I used the voice dialing. It worked fine after that.