It is kind of a crap shoot with asking for bonuses. I asked for a PAD bonus of $5 on one shop and they declined it but on another shop they accepted a $20 PAD bonus. All you can do is ask and if they say no, then so be it.
That's terrible, is this is consistent issue? I have not had any trouble with being paid for my work on other sites.
There are a couple of videos available and a test you can take which will help you learn more about navigating through iSecretShop, Toasha.