Creating a super antenna

I am not sure if this is the correct place to ask this or if there is even a dedicated section to pose questions about these kind of "homebrew" solutions but here it goes.

Ive been mulling over the idea of creating a super antenna by connecting several of the the internal cellular antennas in either parallel or in series. These would be attached to the rear glass somehow ( Ive yet to determine the exact practical method of doing so). If anyone out there has any in depth insight as to how this would or would not work then constructive criticism is welcome.

I have a ATT iphone unlocked onto the T Mobile network, I understand that they do not communicate on all the same frequencies. My issue is that my place of residence must be on the very edge of T mobiles service coverage so i bounce between 2 bars and searching all the time. I have no issues with reception when i am at work in town so i know i do not have a hardware issue, i just want to experiment a little.