[HELP NEEDED] Disabling HD in youtube on SAMSUNG SMART TV 46ES6200

Short and SImple-
I use a BSNL EVDO connection alongside a WIFI router rendering me 1.2-2.5mbps speeds throughout the day,
while using YouTube on my SAMSUNG 46ES6200,I notice it auto plays in HD if the video supports so causing unwanted buffering at times.
(sometimes i get rock solid 2mbps+ without fluctuations,wherein it plays without any buffer).
But when I play some video which has a maximum quality of 480p,it plays lag free and buffer free,
But most channels i follow post full HD videos and watching it is a pain in the ass,
I've been hunting of someway to disable HD so that i could watch videos without hickups.
Is there any possible workaround?
Thanks in advance
for so many months now i can only see 2-3 videos in youtube app history in my tv , earler it was all of history , i thought it will get corrected automatically, but after many months still its only 3 videos max nowadays

any help[ will be useful:)