Any tips for working with Andromalius?

I’ve researched him thoroughly, but I thought it would be wise to ask beforehand, in case there was something I may have missed.
My reason for contacting him is that I was referred to him by an acquaintance as I have had several signs, seemingly from Satan, one being a dream about him deceiving me.
Also, due to this work being for the purpose of looking into into demonic affairs, will the price be higher than that of a normal offering?