Every support mail should have a footer with the managers name of who you can contact. If you don't have that, then any manager from any mail you got from support should suffice.
The other option is to ring support, or update the PMR with the words that you want to be contacted by a manager/supervisor. You should absolutely get a response then.
Failing all that, you can mail me "sod1684 @ ie.ibm.com" (remove spaces) your PMR number and I will flag it for attention for related parties.