Clipper blades for Oster Clippers

I've already bought several, but after using them they don't cut anymore. I have a cocker with short hair, so I end up stocking up on cutting blades that are way too expensive for such little use. I even bought the No. 4 twice and same thing, it doesn't cut anymore, just like the No. 7. Soon I'll have the whole collection—it's a shame, I don't know what to do with them since I can't use them anymore.

Terribly disappointed with this expensive trimmer, it doesn’t do anything that was promised. Out of sheer frustration, I had to go back to using my cheap trimmer.