The problem with the OP XML sample is that, even when viewed/saved via the "download" link (to eliminate the PM line-wrapping), there is still other line wrapping that needs to be undone on several long lines near the end of the file.

Once that's fixed, a simple bit of work with XPath expressions will get you what you want. I posted some sample code for this a while back, here: Re: XPath command line utility....

If you want to try the script posted there, save it as "exp" somewhere in one of your PATH directories, make it executable, and run a command line like this:

exp -p '//Attribute[@name="Agreement ID"]/Value/@value |
  //Attribute[@name="Cycle code"]/Value/@value |
  //Attribute[@name="Subscriber ID list"]/Value/@value' your_file.xml
[download]

(NB: I'm using a bash shell, where it's best to use single-quotes on the outside and double-quotes inside.) When I ran that on the (edited version of) the posted XML data, I got:

15827134
1301
15846291
15613501
[download]

The first number is the "Agreement ID", the next is the "Cycle Code", and the rest are the "Subscriber ID list".

(The XPath expressions for this are a bit bulky, but once you grok the syntax, it's a lot easier than writing code.)