Have your guys ever read the article as below? :) Why I cannot access wireless N range extender by using the domain name? http://www.tp-link.com/en/faq-504.html

Who is your ISP in Iran? If possible, test the SIM card on your phone or a different modem. Try to find the log from C:\Program Files\TP-LINK\TP-LINK 3G Client. Save the log. Send it to...

Your main router supports 2.4GHz band only, right? The benefit is that RE200 can extend 2.4GHz and broadcast 2.4GHz and 5GHz Wi-Fi at the same time. So if your wireless clients supports 5GHz band,...

RE200 is a dual band range extender. 150 Mbps and 300 Mbps refers to the maximum wireless link speed. Since your router is a 300Mbps one, WA850RE should be better compared with WA750RE.

On their website, there is where to buy info? http://www.tp-link.com/eg/where-to-buy/

As I checked its user guide, there is bandwidth control feature and you can Enable IPTV Bandwidth Guarantee. Page 98 http://www.tp-link.com/resources/document/Archer_D5_V1_UG.pdf