From what you have written it is difficult to understand exactly what is happening.
If I read it one way you have loaded a package and it contains a block of code that is currently running and you want to terminate execution of that block of code.
If I read it another way you have loaded a package and it has defined some variables and functions and possibly created some contexts and you want to undefine some of those variables and functions.
Unfortunately with absolutely no idea of what the code is or what it is doing it is difficult tell you how to make it stop doing whatever it is doing at the moment or even if it is currently running.
If you Google for
mathematica unload package
and read through the many results from that you might be able to see which, if any, of those apply to what you are dealing with.