Long residency

Morning ,I’ve applied for student finance for September 2023.Am been asked for proof of long residency from 2001 to 2022 .I previously sent my biometric and home office letter which states reason I was granted leave to remain under private life.It also states am allowed to work and study .
I’ve been on the phone to sfc and every time been given different impressions!.r home office letter and biometric with passport were enough.I then received a response asking for my immigration status from 2001.Now this is showing me that the person dealing with my case doesn’t understand 20 year long residency and it means certain years you didn’t have legal status and the home office grants discretion provided you can show you have been in the country for the last 20 years.Why can’t sfc confirm with the home office on which basis I was granted leave to remain.I spoke to the home office which eloborated that any information regarding my status can be confirmed by them.I don’t have letters dating back to 2001 and am buffled as to why I’ve been given different advice on calls and been asked to show my status in 2001 .I came to the uk in 1998 and never left .It seems like every time I send what is requested am been asked for something else .Can someone clarify what you need to provide as evidence and wether you are able to get in touch with the home office to check long residency