Speaker dosnt work

Go to settings and tools>sounds settings and insure that you somehow did not inadvertently turn off sounds.  It does happen.  The primary culprit is of course master volume.  Check it and all the other sound related settings.  The turn on and off sounds for different actions.

Have a friend call you.  Check if  you can hear them.  Turn on speakerphone  (small button to right of MicroSD slot).
Have friend call you again. 

Once you have checked all possible settings and they are all to "on" and you still have nothing, remove the battery and try the chicken soup of cell phones.

If none of that works it is time to at a minimum call 611 and bump to tech support.  Most CSRs at 611 would have you simply do the above.

If they cannot help you go to a store and see if they have a bench tech.  Larger stores sometimes have one on staff. 

If you get sounds back, let us know what resolved it.  Good luck.