Your situation doesn't sound promising by what you say, but if you give us their name we will see what we can find out about them for you. Also, how did you pay them and how long ago did you pay?
In regards to other companies that offer this type of service, yest there are quite a few, but. I think it's important to really understand what you are going to be getting for your money. I'm not saying they are all bad, but you have to bare in mind that these companies make money from you for selling you a stocked store, so they are relying on you to sell their products to make them money, as per a traditional dropshipper platform.
So you have to be very careful about their prices and marketing strategy, are their prices competitive and what sort of marketing do they offer to drive traffic to the store you are paying for?
If you are going to choose this type of platform, then you need to be sure you are getting decent value. If they are stocking your store with un-competitive products/prices and/or not offering any sort of marketing, then you have to ask your self what sort of value you are getting for your outlay?