If they're constantly calling your continuation bets, then you need to mix in checking when you hit, checking when you miss, and vary the size of your continuation bets when you miss...vary them between 40% and 100% of the pot. If I see that you put in a continuation bet of size x regardless of if you hit or miss, then I'm going to start taking a stab every couple hands to take one away since it's going to be +EV for the times that you miss. To defend, you need to make me less confident that you're really putting a continuation bet in, and you do that by varying your bets AND your betting pattern.

If you are pretty sure they are calling your flop bet to take it away from you on the turn, you should be check/calling ( or check raising) the turn with an overpair ....and betting the turn again with AK.

Ice:
Are you saying that the unimproved AK should bet turn to protect from the suspected steal?

If so, is that really necessary?
You'll be +EV on all their steal attempts from the times you do have something (assuming your raising criteria are high enuf), so wouldnt it be OK to humor them and let them keep up their -EV stealing?

Black-knight:
Don't you think that varying the bet-size for CBs does the excact opposite? As long as the opposition can't discern what kind of hand you have from the bet size you chose, you do fine. I'd rather adjust my missed check:bet ratio than muck around with the bet sizes. But that's just me.

Just a few thots
/Rush