I have the
Optilink OP-XONT 71000 as well. The native optilink firmware will only limit to 100mbps on Excitel network. You will need to ask Excitel to update the firmware on this ONU. Following this it will get 300mbps.
I learnt this the hard-way, after doing multiple anydesk session with their customer support. This is how the web interface will look like (check the software version with yours),