I suggest you contact the attorney that represented you at your trial or plea hearing.
Without knowing the specifics of your case (and I don't want to know more), we are at a disadvantage.
But, even if we knew more, we can't help you.
If there is any recourse, it is with the court where you took the plea.
In fact, you were given plea documents and various waivers at the plea hearing.
I suggest you dig them out, before you contact your former attorney.
More than likely, you pled to a lesser or included offense under the originating charge.
You could also reach out to the persecuting attorney and inquire what their records show.
Don't hold your breath, courts are reluctant to undo their mistakes, assuming a mistake was made in your case.
This has to do with the doctrine of res judicata (let the thing rest).
But, I've seen some corrections taken in my time, not many, nevertheless a few.