Apple iCloud Lock Makes My iPhone 17 Pro Almost Unusable

I am using an iPhone 17 Pro linked to the iCloud account with the email address christinatw***@gmail.com, which I purchased from Walmart through an AT&T sales representative in Austin. For the past five days, I have been locked out of my iCloud account after forgetting my password, and my phone has become almost unusable. I can only receive calls, but I cannot make calls, send messages, or use other services because the device keeps requiring the iCloud password. I am on a prepaid plan with AT&T and I have already tried to follow the instructions given by both Apple and AT&T/Walmart customer service. I attempted to reset my iCloud password twice, but each time I received a message that they could not complete the transaction at that time. I believe the procedures are supposed to be simple, but I am afraid of making mistakes and feel that I may have done something wrong in the process, so I could not complete the steps they described. As a result, I am still locked out of my account and cannot properly use the phone I bought. I request that Apple urgently assist me in resetting my iCloud password and unlocking full access to my iPhone 17 Pro after verifying that I am the rightful owner of the device and the account associated with the email address christinatw***@gmail.com. I would like clear, step‑by‑step support so that the process can be completed successfully and my phone can be used normally again.