Hikashop redirect to payment gateway url with a POST, but we need a GET!

-- HikaShop version -- : 4.6.0
-- Joomla version -- : 3.10.6
-- PHP version -- : 7.4.3
-- Browser(s) name and version -- : Chrome 90.0.4430.212

Hello!
we created a "payment plugin" for hikashop environment. Plugin call a custom WS that return a the url for the paymente gateway.
As the example we had follow, in the "onAfterOrderConfirm" we set that url into $this->gateway_url.

Then i don't know what append, but if url point to a bank gateway that accept a POST call, everything goes well.
If the url point to a bank gateway tha only accept a GET call, then we got an http error "POST is not allowed".

How can we manage that?

The best would be to have a custom plugin parameter where to set GET or POST options as needed, but i don't know then how to say "hei hikashop! do a GET for this case"

Thank you very much.
Regards,