How Can I Spend Testking Credit?

Buddie,

I won some houndreds of USD credit from Testking.com and very confused on how i could convert it to naira to enable me pay for my microsoft certifications.

I was told by Testking.com that it could be only spent for their product and i don't think i need any of their product for now.

please, could anybody advise me on the best way to spend this credit?

Thanks