I have browsing About CobinHood, and I'm not find if they charge trading fee, but maybe this can help you!
COBINHOOD collects 5% of the funding raised from the ICO as an underwriting service fee.
You can learn more at this : https://cobinhood.zendesk.com/hc/en-us/articles/115002483452-How-does-COBINHOOD-earn-revenue-if-we-charge-ZERO-trading-fee-

Thank you