I am trying to create an app that has a similar feature to apps like Whatsapp, Messenger, Uber that allows you to call another person. I am not seeing the option to do this in Thunkable. How is this achieved?
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There is no easy way to do this. You would have to either hire someone to do this for you or learn all the tools to build such an app. There are of small details that will determine how difficult it will be and what things you will have to learn. I would begin with planning out how the app works in detail. For example, creating a list of all the features you want your app to have.