After exam/bill, do I have right to change from Insurance deductible to Self-pay??

Good Morning all,

I live in NY and on my partners insurance, currently as a stay at home dad. Last year had an ultrasound and before I pay, they ask me if I want to go through the insurance or self-pay, because they didn’t think insurance would cover (due to deductible). I called insurance at the time, but it was after hours, so no help. As I sit there not wanting to pay the $500 self-pay vs the unknown charge they were going to charge my insurance (they could not provide me with a dollar number at that time), they lady at the desk said that if the insurance does not pay, I can self-pay after the fact.

Fast forward, I get billed from the ultrasound place for $2500 due to the insurance deductible not reached yet. I called and asked to go the self-pay option instead of the $2500 bill due to insurance deductible. Their billing dept called back and said they can reduce by half, so $1250 I can pay. I explained my situation and kindly asked again if I can change to the self-pay route as that was presented to me as an option to pay before the ultrasound.

No response back. Fast forward to now and a collection agency is trying to get the $2500. They are saying that I cannot change the payment from insurance to self-pay once they run the insurance. Which is the complete opposite of what ultrasound place presented as an option on the date of ultrasound. Ultrasound place did not mention I cannot change the option, only now did the collection agent say it. Collection agent is also saying on the date of exam, I was never presented with the option to self-pay after, if insurance did not pay.