lol, how pathetic. Engineer on Carpenter Visa ? So you are also lion on monkey visa (Read http://www.qatarliving.com/advice-help/posts/regarding-salary-slip ).

You shouldn't have agreed this profession on visa. anyway one of my friend had similar case and he successfully managed to get it changed but it took really long time (due to this attestation etc. ) to get his family visa.
Start doing one by one as stated in above comment. Good luck :)