I purchase videos all the time using a University issued purchasing card
(Master Card). The card was originally restricted to particular vendors
who use a specific set of MCC's or merchant codes and it can NOT be used
for entertainment or food purchases.
Althought the food restriction is no problem, the "entertainment"
restriction began to give me trouble immediately due to the wide variety of
vendors we patronize. (Many video retailers also sell video games so my
card was being refused all over the place!)
I contacted our University Accounting office in charge of this purchasing
card program and pled my case, very convincingly I guess, because they
authorized my card for any of the MCC codes on their list which had
anything to do with video, laser disk, cd-ROM or DVD and I haven't had any
The bottom line, your trouble probably has little to do with the content
of the materials your vendor distributes and everything to do with their
MCC or "merchant" code. Hope this helps.