Replace oxygen sensors?

I have a 2000 toyota camry v6. My check engine light came on. I ran the code and it was p0135 which is bank1 sensor1. I switched it with the other sensor to make sure it was not a computer problem and cleared the code. When the light came on again I ran the code and it said p0155 bank2 sensor1. So the code was following the bad sensor. So I went and bought one from the toyota dealership and replaced it and now it keeps running a code on the new sensor. Any possible solutions

I hAVE A 2000 Toyota Camry. I have replaced a Oxygen Sensor in front of the Catalytic Converter. The computer reader said it was this oxygen sensor. After replacing the sensor and resetting the computer for the check engine light to go off, I had driven the Car about 150 miles and the check engine light came on again. I checked the car again and it said it was the same sensor that was bad. I replaced the sensor with a Bosch Oxygen Sensor thinking maybe I had a bad part the first time, but the check engine light is on again. Do you have any suggestions? The car does seem to hesitate when the check engine light is on. Could bad gas have caused the problem in the first place. Before the check engine light came on, the day before I had filled my gas tank @ a different gas station, and the car seemed hesitate to start. Please advise.