United MileagePlus (Consolidated) - Combining travel credit coupons and ecert?

Is it possible to combine travel credit coupons and an ecert? I was issued the coupons while I was still at the airport, but issued an ecert after I got home for an additional $100. On the coupons it says they are not combinable with any other vouchers or credits. Since all of the coupons and the ecert were issued for the same VDB shouldn't UA be able to allow the combining of the two? Any advice, guidance or creative ways to make this happen will be greatly appreciated.

If you wanna know how I received to different types of compensation the story can be found http://www.flyertalk.com/forum/united-mileage-plus-consolidated/1233754-vdb-ord-ua-obligated-honor-its-vdb-offer.html

They cannot be combined in their present format.

If you want to pursue it, you'll have to see if UA would void the e-cert, return the paper, and issue you new paper for $400.