soap request doesn't replace variable

Hi, 

I'm trying to build a script that will open a file of phone numbers, 1 per line. It then reads in each line and add each line to an array. I add the array to the context.

def msisdnList = []
new File("C:\\Users\\Jerry\\Documents\\MVNO\\soapui\\msisdn_99.txt").eachLine { f ->
if (f != null ) {
     
     msisdnList.add(f)
     //log.info f
}
}
if (msisdnList.size() < 1) {
   testRunner.fail("No request msisdn")
}
context.put('msisdnList', msisdnList)

In the next step, i check i can read the array, which works fine:

log.info "MSISDN: ${context.get('msisdnList').last()}"

In the failing step, i try a soap request which (envelope and header skipped) like this:

     <ADD_SOC_REQUEST>
         <MSISDN>${context.get('msisdnList').last()}</MSISDN>
         <SOC>SMPGL2</SOC>
      </ADD_SOC_REQUEST>

running this, I get error because what goes out is 

<MSISDN></MSISDN>

Does substitution work in SOAP request?

Thanks.