how to unlink compositon layers in after effects

How many levels of nesting are in the template?  You'll have to drill down through until you find the proper text layers to change.

I'll assume that when you duped the precomps in the project window, you renamed them and used the Replace Footage command to change the old precomps to the new ones.

An easy solution would be to

1) create an new, empty project

2) import your template project 2 times into your new project

Now you have two duplicated of the entire template in your project and they are completely independent.

If you just want to duplicate specific comps with their precomps, you can also try True Comp Duplicator

http://aescripts.com/true-comp-duplicator/

Use the project flow chart and then drill down to the last instance of the text. If that comp is common in all of your other comps then you did not duplicate the nested comps. Simple as that.

Here's a step by step. First open one of the duplicate comps and then choose to view the flow chart. Select the text layer that is giving you problems in the flow chart and drill back to the first instance of that text layer. Reveal that comp in the Project panel and note the name. Go to the project panel and duplicate that nested comp. Now open one of your other duplicate comps and follow the same procedure until you get to the original text comp. Use the replace footage command to replace the original text comp with the copy you just made. Now change the text comp in the duplicate and you'll see that the text in the original did not change.