I think the lack of replies is because they are possibly not what I would call a mainstream offshore agency as far as ROV goes.
That’s not to say that they may be a problem. If all looks good, you have a dialogue with them by email/phone, the rate is as it should be, plus there is no negative feedback from here, then give them a try.
Later, you could hunt out this post and report any findings based on your experience. This would be of benefit to other members around here.