Employment verification Letter for PEPM process - Capital One

I'm an ex employee of Capital One and need employment verification letter for my PEPM process. My immigration attorney asked me to get a detailed letter on my roles and responsibilities from my previous employers. Has anyone got a employment verification letter from Capital one either from HR or manager before, if then what was your approach.

Also can anyone share me the HR Dept phone number or email I'd that I can use to reach out to the HR Department.

Thanks