Fixed table rate shipping and UPS charges.

I have a strange problem with shipping.
We charge fixed table rate for domestic shipping up to 50$. anything above it being given a free shipping via UPS or in addition customer is given 3 choices: ground, 2nd day, 3rd day shipping) and UPS set to residential rates.
Every once in a while (about once a week) i see customer, that spends over 50$ suddenly is being charged for ground shipping simply because he doesn't see the free shipping option. took me a while to figure out that the problem is customer's given shipping address. Customer don`t see the free shipping option, when he puts PO BOX address, or non residential address. The question is... how to make the store not to charge for shipping if customer spends over 50$ disregard of commercial address that they provide?
1.3.9h version is used.
thanks.

I see there are no answers, so ill try to be more specific.
My UPS settings are:

Enable UPS Shipping
True
UPS Pickup Method
RDP
UPS Packaging?
CP
Residential Delivery?
RES
Handling Fee
0.00
Handling Per Order or Per Box
Box
Tax Class
--none--
Tax Basis
Billing
Shipping Zone
--none--
Sort order of display.
2
Shipping Methods:##
1DA, 2DM, 2DA, 3DS, GND, STD, XPR, XPD, WXS

My table rate options are:
Table Rate

Enable Table Method
True

Shipping Table
49.99:7.00, 1000:0

Table Method
price

Handling Fee
0

Handling Per Order or Per Box
Order

Tax Class
--none--

Tax Basis
Billing

Shipping Zone
48 Lower States

Sort Order
1

Now can you please tell me why some of my customers that live within 48 States, sometimes not see Shipping cost 0, if spend over $49.99 , instead they see UPS Ground shipping cost. Some are provided PO Box addresses, some regular house/or apartment addresses, some business addresses, but they are all within 48 Lower States.

no thoughts? please help, this is really an annoying problem.

Have you a link to your site?

Is it a matter of the Customer does not "see" or chooses not to "select" the Table Rate when it is $0.00 and just wants a different UPS shipping method?

we been calling customers asking, they say there were no 0, (it is hard not to see, we made it red color)

Off the top of my head I am not seeing the problem ...

Continue to try to find a pattern on this for the Ship To and the Products in the Cart when this happens ... maybe something will jump out on this ...

If you look at your Zone Definition for:
48 Lower States

How many Zones are in it?

Ajeh:

Off the top of my head I am not seeing the problem ...

Continue to try to find a pattern on this for the Ship To and the Products in the Cart when this happens ... maybe something will jump out on this ...

If you look at your Zone Definition for:
48 Lower States

How many Zones are in it?

We are using the written script i found here for 48 Lower States, and all this states are included in it, because most of customers that are from this states are not being charged. First i thought they just select ground shipping as a choice, then i thought that customers with funky addresses like PO Boxes or business addresses are being charged, but last couple times there were residential addresses as well, i even test to go trough estimate shipping by adding same things to my shopping cart that they are buying, using their addresses and i do see the 0.

the zone definition name is 48 Lower states+DC:
In details:Number of Zones: 49
Description:
48 States + DC

Also i made sure that customer cant manually write the state to avoid any mistyping, its being selected from drop down menu.

I cannot reproduce this issue on your site nor on a test site ...

Maybe install the Master Password encrypted add on plugin and the next time that this happens, login to the customers account and test an order with the same Products and address and see what you see ...

NOTE: remember to check their shopping cart to see if they have any saved Products in their cart and to remove the Products you add to test this before you log out of their account ...

I did logged as customer put their shipping info and i cant reproduce it as well, i see the free shipping. But i did changed wording from Table Rate (Best Way) to capitalized "BEST RATE" 3 days ago and did not get any new ground shipping yet. crossing fingers and hoping this was a customers choice, rather than a system error.

can this issue be related somehow to a combination of certain product and something else, like address? because i seen in 3 different cases i see there is a same product purchased..