Can I apply for change my i94 status to work on H1b visa?

In general when an individual is in the U.S. and they petition for an H-1B then they are granted a change of status to H-1B and they get a new I-94. If your company did not ask for a change of status then you likely received an approved H-1B but you did not get the new I-94. If you leave the U.S. you will have to go for a stamping to return in H-1B status. You may be able to use the B-1/B-2 to effectuate an entry (assuming that the visa stamp is till valid) but then you will not be able to go on the payroll of the U.S. company. The best thing to do if you leave on a trip is to plan to do your stamping at a U.S. Consulate Office abroad. You can do this either in your home country or in e thir-country. If you do it in a country other then your home country the process is called TCP or Third-Country Processing. Often these cases are placed under Administrative processing unless you have a good reason why you are doing the TCP process.