Hi! I'll start by saying that this is a tough one. I personally employ several sales reps, some 100% commish while others take te bigger of two: commissions for that period or a predetermined hourly rate (if they feel they won't do as good that week)

With that said, these type of jobs tend to pay only on production, merit based, not presumed value. But that doesn't mean you can't work around it.
Try:
1. Use a speculative wage offer approach... This is you identifying gaps in the firm and offering solutions in lieu of the opportunity and pay increase...
2. Speculative application doing the same at another firm...
Assuming you are barely starting with the firm i would serioiusly recommend you do your best during the review period, while planning to meet and extend your offer to the firm... This is done for high corporate entry level positions as well and tends to work if you pitch yourself right...
Focus on the holes in the firm you can fix,
How much money that will save or generate considering your wage, and the credit the hiring manager will get if all goes great

Good luck