As a valued customer, you are eligible for savings of $300.
Whatever follows the "as a valued customer" should be the noun that is the valued customer, i.e., "you" not "we."
Believe it or not, my university diploma has the same type of mistake. It says something about having pursued my studies with diligence, the board of regents is pleased to present me with... as though the board were the ones who had pursued my studies.
It's a classic example of a misplaced modifier.
[not a teacher]