Even if the protection was really good - you are paying a dealer markup on something you can easily (and probably better) get done yourself. It may be more convenient but if it is costing (including the dealers markup) less than what professional dealers charge for proper protection then it won’t be as good. Ask the dealer or the company how long is the guarantee - if it’s only a year then it isn’t very good protection.
Also, ask how long the process will take - it should be longer than 1 day. As Richjess01 says, proper protection starts with a correction of the original paintwork and then applying the protection and then curing - can’t really be done in a day.