Sub-contractor with no contract

Our company goes into alot of projects and hires sub-contractor, and the vast majority of time not having any contract or terms in place. The majority of times everything works well.

On this instance, we recievd the first valuation from the subbie and noticed that there were additional costs included which we were not aware off. That valuation was a complete mess so those costs were removed, and we were told they would be sent separately.

That was 4 months ago, and I have been chasing numerous times to get these cost so we can confirm with our clients about them.

Without having a contract is there any way to enforce them into sending them quicker, or even just disregard them.