University is not issuing me my convocation certificate
Assuming that it is a lack of communication that is causing your problem, you need a way to create the needed conversation to get the problem resolved. 

I'd suggest sending an email to both the department head and the college office explaining the difficulty and asking for a resolution. This should be one mail, addressed to both offices so that you put them in direct communication with each other. 

You may learn something from whatever response you get from either or both parties. If the problem goes beyond communication, you need to know that in order to figure out what else might be done. 

But you need, also, to phrase things respectfully, even if you don't feel it. Calling names such as you used in an earlier question here will only get you ignored.