Thank you for joining the thread, @Malik_MY. I'll point you in the right direction for support with your concern about canceling a QuickBooks Online (QBO) subscription. 

Since you're unable to proceed without the registered mobile number, I suggest contacting our Technical Support team for further assistance. They can pull up your account within a secure environment, and sort out this issue. 

 Check out this article for the steps: QuickBooks Online Support. Please take note of their operating hours, so you know when they're available. 

After you successfully canceled your subscription, I suggest you open this article: What happens to my QuickBooks Online data after I cancel? It has a list of data availability for your QBO company, as well as export policies.

You're always welcome to post here in the Community if you have other questions. Post a reply in the comments below, and I'll get back to you. Have a pleasant day!