〜へん/〜ひん means “not” (Kansai). Kansai makes verbs negative with へん instead of ない: 分からない → 分からへん, 言わない → 言わへん, できない → できひん. You will hear it from almost any Osaka-based comedian.
Is 〜へん/〜ひん rude? Who can you say it to?
With friends: OK. With coworkers: careful. With a boss or teacher: avoid. Kansai dialect. Casual.
How common is 〜へん/〜ひん in real speech?
In 1,905 live comedy routines, 〜へん/〜ひん appears in 359 lines from 61 comedians.