Your vehicle doesn’t have seven O2 sensors. There’s only two. One before the catalytic converter and one after the catalytic converter. And the only one that can have an effect on engine performance is the O2 sensor before the catalytic converter. So if they’re saying there’s a problem with an O2 sensor, the one before the catalytic converter has to be it.
But if you could provide the actual diagnostic code(s) that’s stored in the computer it would narrow it down. Parts stores like Auto Zone will pull codes for free.
Tester