Allsec Technologies — Not giving my experience certificate

I was an ex-employee of Allsec. I am denied my service letter telling that i have not completed my exit formalities. But I served my notice period and had an exit interview too. Im not aware of any other exit formalities. Now its almost 8 years, whenever I ask them about my letter they give a reply its not possible, Now im in a situation where my job is affected because of this.They still deny my service letter telling that i absconded. My manager still remembers that i did not abscond. When I asked is there anything which can be done to resolve this issue the HR Anitha says I can fake my resume by not putting my Allsec experience there. Is this how a HR should answer and she is very rude too. Im so disspointed and curse myself for joining Allsec turning off offers from other companies Athira Emp#11063