Shipping price issue

[cyris69]

Ok, I'm using the newest prestashop v1.5.5. I have my USPS module and api setup and it calculates pricing correctly by weight.

 

However, I want to offer free shipping on some items and not others. 

 

So lets say it this way

 

Catagory A, I want this not to be included in shipping calculation so if someone just adds an item from 'A' it will not affect anything and calculate as free.

 

Now my issue is that with USPS module enabled no matter any weight given it costs whatever it calculates a flat rate and I want this to not happen.

 

But lets say I want items in Catagory B to not be free shipping and calculate by weight. But that person has an item from Catagory A in the shopping card as well. When this happens a fee is calculated for 'A' in addition to 'B' even though it has a weight of 0. Or in my case when fiddling around it produces two options Free Shipping bubble and the USPS carrier bubble so one could just choose free and not the calculated USPS bubble.

 

I'm sorry if this sounds confusing the way I described it.

 

I sincerely thank any who help me!