If you don't want a plea bargain, don't do it. You have an absolute right to a trial.
PI is a class C misdemeanor in Texas. The worst that can happen is you have to pay a fine. You don't need a lawyer, although of course you're free to hire one if you want. If you have a trial, the jury will listen to both sides - your side, and the cop's side - and then decide which one they believe.
You can't reduce a class C, because it's already the lowest level offense there is. You can get a deferred disposition, if you plea bargain, or an acquittal if you win at trial. Either is eligible for expunction.