Missing Advantage Rewards - complete runaround by support

Back on 5/8/2017, I called in to the business rewards support line to report several orders for which I was missing rewards credit.  This issue is still unresolved.  Following is a summary of events:

• I am missing rewards credit for approximately $22,500 in purchases I made from December 2016-March 2017
• I *did* receive credit for some orders I made during that period, but credit was not issued for some of the larger purchases I made during this period
• I compiled a list of all orders and purchase IDs for which I did not receive credit
• I called in to the Advantage Rewards support line, but was told that if I had a big list I would have to send in an email request to us_05_care@dell.com
• I sent an email detailing the situation to us_05_care@dell.com
• The response I received was as follows:

Hello Jay,

I’m unable to assist you on request. I highly recommend you to contact the finance department for assistance.  

Thanks

Nedelka Brown " Nelly "
Customer Care Analyst
Dell |Global Business Operations
nedelka_brown@dellteam.com

• I replied, asking how to contact the “finance department”
• I was told to call 866-454-0985.
• I have called that number twice.  Both times I have been on essentially infinite hold – automated attendant answers, says an agent will be with me shortly.  Today I decided to just wait on hold until someone answered.  Eventually the line just disconnected.
• I sent ANOTHER email on 5/12 to every Dell support email I could think of; all I received in reply was "thank you" from Nedelka Brown on 5/15.  
• On 5/16, Nedelka Brown emailed and said she said she was escalating with the mysterious "sales and finance" for "proper assistance"
• 5/25 I emailed again, asking for an update
• 5/25:  Nedelka Brown responded with "Request will beforward to the finance team" (sic) (again?)
• 5/29:  One last email from Nedelka Brown - "thank you"
• One last thing - Nedelka Brown's email signature states "How am I doing? Please contact my manager at Gricelda_Roter@dell.com for any feedback."  I've tried contacting this person - email always bounces.

I've ordered quite a bit more from Dell since I sent the initial email.  Additionally, I buy HDDs, memory, etc. from Dell for a bit higher price than I could get elsewhere *because* of the Advantage rewards.  It is starting to seem that is a total waste of $.

Anyway, I ran across this forum, am hoping there might be some possibility of resolution here.