You are in a situation where you need to override the price of an item on a Contract.
You have the ability to type a different price than what Omni Price pulled in.
In the Sales Transaction Entry window, once you enter in the desired price and tab off of the Unit Price field, the following warning message will appear, which you will click Yes to continue.
Keep in mind, however, that overriding the Unit Price will break the tie to the Contract that it would normally use for that Item, which is what the warning message is stating.
Omni Price does not have a way to select that a different Contract be used for a given item.