Am I Legally Obligated To Help My Job Who I Was Let Go From Six Months Ago (tx)

Location: Texas

A little background: I was laid off in January as part of a large workforce reduction. I worked as an Accounts Receivable clerk, and my responsibilities were transferred to another employee after my termination. I have since found employment elsewhere.
While I worked there, we used Square to process customer payments. My boss originally had her phone number set up for the two-factor authentication (2FA). Because she often wasn’t available to provide the verification code when needed, she and our IT department decided to change the 2FA phone number to mine. I didn’t make that decision myself. I was told they were making the change so payment processing could continue without delays.
Apparently, after laying me off, they never updated the account to remove my phone number. They are now unable to access the account.
Over the past several days they’ve repeatedly called me while I’m at work. They also asked a former coworker’s daughter, who I’m close with, to reach out to me. This isn’t as simple as texting them a verification code. From what I understand, it would require me to contact Square, verify information, and authorize the removal of my phone number from their account.
I don’t have the time during my workweek to handle this, and I also don’t feel comfortable getting involved. Before my layoff, they made accusations against me that I found both hurtful and completely unfounded. Because of that experience, I don’t wish to have further contact with anyone from that office.
After I blocked their phone numbers (which I did shortly after my layoff), they emailed me. The email states that if I don’t respond by July 8, they will document my lack of cooperation and consult with legal counsel.
My question is: Am I under any legal obligation to assist my former employer with regaining access to their Square account when they were the ones who chose to associate my phone number with it and failed to update it after terminating my employment? Can they realistically pursue legal action against me for refusing to help?