can escrow require me to pay more in closing if they made a mistake in their calculation?

We closed on our home on Jan.27th. The escrow company contacted us after and informed us that there was a miscalculated and there is a shortage in what we paid and we owe more money. The resolution was that escrow pay 60% and our realtor agreed to pay the remaining. The escrow officer took it upon himself to contact our homeowners insurance company to try to get our refund check released because there was a difference in what we paid and what the actual annual homeowners insurance cost was. The escrow office is threatening to send the 800 that they contributed to their mis calculation to collections. Can they do this if the home has already recorded and closed? Also was it ethical of the escrow company to contact our homeowners insurance company and intercept our refund check?