Before My shopify free trial ends, I installed an app named "Okendo", but after tried 2 days, I do not want to use that app and install that.
When I pay the shopify basic plan, I was charged by that app. So I install that app(I pay for it after all). But the Okendo store workers say I have not selected a plan.
I got confused, where the money goes if they did not receive it? How should I get my money back, because I do not want to use that app anymore.
Apps from the Shopify app store will have their own billing cycle which is separate from the Shopify monthly subscription. Once you install an app the billing cycle will apply to the account once the trial for the app is no longer valid (if a trial came with the app) and will charge the account. Removing the app before the trial ends will be the only way to avoid a charge; however, if there is already a pending charge on the account then uninstalling the app will not remove the charge.
From the sounds of it, your store would have had the app installed long enough to have it charge the store, or initiated a onetime charge within the app. Even though the app was uninstalled, the app charge would still be valid and would require the app developer to approve a refund for the app so long as the app is removed. The situation is a bit confusing if the app developer as mentioned they are unable to locate the charge so I will want to verify the store to better understand the situation. I have sent you an email titled "Shopify Forum Support" requesting further information. If you can reply to that email as soon as you're able then I can review the charge and help with finding a solution.