Ahmed - there are no specific organisations for that purpose. However, with grant applications, it is becoming more common for researchers and research teams to request funds for open-access dissemination of findings - and funding bodies are increasingly accepting of this. Many journals offer 'discount' depending on country of origin - or classification according to level of development. Best to examine several of your target journals and look at the author instructions and processing charges - and then you can make your choice.

See academia.edu

but there you have to subscribe it.

I have noticed that several OA journals with higher reputation in their field offer certain discounts for authors with financial constraints, if the submitted paper is accepted for publication. However, be aware of the predatory OA publications.