If your not happy then i definately think it can't hurt to write a letter of complaint, it doesn't need to be in detail but just explaining that your experience was not great, the sonographer did not communicate well etc.
You could always get a referral from your Dr to get another scan somewhere else but it may end up costing you and i'm not sure how many they allow so close together.

I hope you can still enjoy the fact you got to see your little one (even if it was only 3 times) and that you know he or she is healthy.

GL with it all.