personal hotspot missing on iphone 4s ios 6.1.3

I have been trying everything that is possible.even a restore or the ios.

I can't understand why on my HTC i can activate my hotspot and it works perfectly using the same sim that is inside my iphone 4s...

is there anything wrong with my iphone 4s?I bought it second hand,it is unlocked to all networks...

what the **** is wrong with this hotspot?I am getting obsessed of it:(((

especially when my internet connection drops...then I'm dead,no internet at all on my laptop and I can't connect it through the hotspot because It doesn't have that hotspot.

basically i reseted every setting.

nothing worked at all.

then i restored the ios

nothing has changed

i am using a TESCO UK sim,I am on contract,I have internet,as I said I can activate the hotspot if i put the sim inside my htc..

does anyone have the same problem?

please help!!!