For future reference, you only really need a single account for life. Keep a record of your account information in a safe place.
I am not clear what you mean when you say Apple "blocked the new account details". Do you mean they have disabled the new account? What is the exact error message? Your next steps depend on what kind of "block" (a term Apple does not use) this is.
Your best chance is recovering access to the old account.
For help with a forgotten Apple ID (this is likely an active email address or one used in the past), click here --> If you forgot your Apple Account primary email address or phone number - Apple Support
For help with a forgotten Apple ID password, click here --> If you forgot your Apple Account password - Apple Support
If you find you can’t sign in, reset your password, or receive verification codes, you can request account recovery (get Apple’s own instructions in this article: How to use account recovery when you can’t reset your Apple Account password - Apple Support ) to regain access to your account. Account recovery might take a few days or longer, depending on the specific account information you can provide to verify your identity. One tip to using account recovery it to look for options in small blue letters beneath the normal log-in items if you cannot complete the requested information.
Here are links to posts by Community contributors which provide additional detail about the account recovery process and what to do if you do not receive a text or call: Activation Lockout Issues - Apple Community and How can I reset my Apple Account password? - Apple Community and How to delete Apple ID when you can't log… - Apple Community This thread outlines the multi-step process and final recovery —> My Apple ID is locked, how do I fix it? - Apple Community , and this one about things you should and should not do while waiting —> How can I recover my Apple ID after multi… - Apple Community
If you cannot get access to the account, Apple can completely reset a device if a person can provide sufficient evidence of valid ownership. This is done online* at: Activation Lock support request - https://al-support.apple.com/#/additional-support Apple says, "Proof of ownership documentation is required," but does not provide many details in the article as to what is acceptable proof. Prior to this official service Apple typically required the original receipt** issued by Apple or an Apple Authorized Reseller and documented provenance (so typically it would be the first owner who does this, or a descendant with legal proof of ownership transfer). Note that while this will let you get use of the device again, it will not help you with lost access to an account.
* There is a special link for this service. To save time you should use it instead of https://getsupport.apple.com/ .
**Apple recommends you keep your receipt after you buy an Apple device. --> Keep your receipt after you buy an Apple device - Apple Support
