"If I stream music let's say for 4-5 hours a day at work"
Get a cd/mp3 player.
I'm just starting to look at ST, and perusing here and at hofo, etc, I see folks wanting to use their phones instead of TVs,mp3 players, etc. Probably old fashioned but I never have the earbuds in when I go out for a walk, ride subway, etc. It does not surprise me that carriers are setting limits, however vague. Have some sympathy for those of us who only use 200mb on a bad month. All this costs money.