The worst possible behavior of a restaurant

Got double charged the last time I was there, was told the next meal I get would be reduced by the amount double charged if I show the proof. When I went the next time, I showed the proof with my bank statement and they did not fulfill their promise. When the bill came I refused to pay the full amount so they locked us in the store and did not let us out. The police then arrived and I explained the situation and finally left.