Want to modify alphabet filter

Hi,

This is my URL
https://lemail.info/ATCO/for-test/?orderby=title

Here I am using alphabet filter.or example if I am clicking on alphabet “A” it returning all the product contain “A”, but I need to filter only product start from “A”.

Ref URL : https://lemail.info/ATCO/for-test/?swoof=1&pa_alphabetic=a

Please help me and let me know where I need to edit.

Thanks,
Debashis Pati