I HATE this about packaged vendors. So many are unresponsive. I'd let them know up front that you hadn't signed anything with them and that a lack of response in a timely manner seemed to you to be a lack of interest in photographing your wedding. You also need to contact the resort wedding coordinator and let them know what happened. If people don't tell the resorts this type of stuff the vendors can go right on getting away with it, and it sounds like your resort needs to find vendors who are more professional.
I agree that you should see about getting credit and not using their photographer. If the resort refuses I'd suggest simply asking to not have a resort photographer present. You are simply giving them your money, but then the resort will get the point that you have no interest in working with people that can respond. If it were me I wouldn't want to work with the resort photographers after acting so unprofessional, and I wouldn't want to give them the opportunity to use my wedding to expand their portfolio and/or samples.
If you really want to use the resort photographer, and not burn any bridges with them, just tell them that you have a friend who is also a photographer coming to shoot the wedding. They don't need to know the details that you are paying the destination photographer etc. That way you can still use the hour of the resort photographer's services.
Either way, the resort photographer isn't going to be completely happy. Option one straight out tells them they were unprofessional and you don't want to work with them. Option two means they will be losing money in print sales if that's what they offer for expanded packages.
Personally, I would almost never use a resort photographer. They tend to not be well trained, only offer high priced prints, and not a lot of photo coverage. There are a few exceptions to the rule, but generally speaking that is my thought on the subject.