How have you been trying to chat with support? This is a worldwide forum and we have no idea where you are. Not all countries offer the full range of support options.
Refer to this page for Apple Support features ➔ Contact - Official Apple Support
Select from the presented options until you find a solution for your issue, or see if there is a chat or phone call contact method offered lower on the page under “Get more help” (you sometimes have to narrow down the options multiple times before this is shown). If you do not see your issue, keep experimenting with any series of selections until you reach one that offers a chat session or a telephone call and get the representative to redirect you.
This support article has various country telephone numbers for contacting Apple for support and service ➔ Contact Apple Support - Apple Support Scroll down to “Connect with live support”. If your country is not in the list, go to the “Other countries” entry at the end of the list. Not every country has telephone support, and phone numbers may only work when calling from the same country.
For chat, you can try using the Apple Support App —> https://apps.apple.com/app/apple-support/id1130498044
If you want to cancel a subscription you have to prove you are the account owner and not somebody trying to play a mean trick on somebody. So your basic issue sounds like account access. I suspect you are having problems because of two factor authentication and not having a trusted device. Refer to: Get a verification code and sign in with two-factor authentication - Apple Support In that case you need go through account recovery. While you are welcome to go to a store I suspect they won't be able to actually do anything for you there since this is all online.
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 is 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 https://discussions.apple.com/thread/255909322?answerId=261058302022 and https://discussions.apple.com/thread/256188713?answerId=261688110022. This thread outlines the multi-step process and final recovery —> https://discussions.apple.com/thread/255733423 , and this one about things you should and should not do while waiting —> https://discussions.apple.com/thread/256148234?answerId=261595361022
If you cannot recover the account, you may at least be able to regain use of the hardware again for use with a new account. Refer to How to remove Activation Lock - Apple Support for the various ways to remove an Activation Lock. If you have the necessary information you can do this yourself, otherwise Apple can completely reset a device if a person can provide sufficient evidence of valid ownership. Check the requirements and steps at: Activation Lock support request - https://al-support.apple.com/#/additional-support Apple says, "Proof of ownership documentation is required," but does not detail what currently constitutes proof other than it “must include the product serial number, IMEI or MEID.” Apple may typically require the original receipt* issued by Apple or an Apple Authorized Reseller. If Apple resets the device this will give you access to the device but won't restore access to the account used to lock it. There is nothing that can be done to expedite an Activation Lock request.
*Apple recommends you "Keep your receipt after you buy an Apple device" --> Keep your receipt after you buy an Apple device - Apple Support