Is there a users manual available somewhere that I can download?
I've searched the web and the only manual I could find for UMX phones was for the model number U671C. Based on the model pattern, I believe that it's actually the same as the U673C with minor changes.
You can download the manual in PDF form from the following website: https://s3.amazonaws.com/tpassets.devicebits.com/pub/254601/docs/U671%20English%20UG.pdf
Note: Here is a list with PDF readers that you can install: http://software.informer.com/search/pdf+reader