Your data is yours; that should never be up for discussion. If any provider says otherwise, don’t walk away; run!
But… there are a number of things you need to be aware of. While you use a cloud service it enables you to manage and process your data in various ways, and when you stop using that system you lose the functionality and features that it has been providing. You must export your data before you cancel your account in order to continue to use it because in line with data protection legislation the provider will delete all copies of your data after a short time.
Consider the example of your online bank. Your money is always your money – you can withdraw it at any time, print statements, pay bills, export transactions and transfer money to other accounts. However, if you stop using that bank’s services you must withdraw your money and you then lose the ability to make further payments, view statements, etc. You should print off or export all your statements and transaction activity before you leave because you once you cancel your account you cease to be a customer and the bank will no longer provide any services to you.