Find a dentist that'll actually do x-rays and show you the cavity on them. Mine does that. The cavities show pretty relatively easily on x-rays because the tooth density is compromised.

If you are in pain, they either damaged the nerve which is bad as that could require a root canal eventually. Or they failed to clean out the cavity and it's infected. Either way, you should experiment with finding a dentist, perhaps go in for a cleaning every 6 months to check a dentist out.

At not point are you obligated to do a cavity filling unless you are comfortable with it. Just decline any additional services beyond the cleaning.