*HIGHLY URGENT*: VISA EXPIRING IN FEW DAYS, NO COS ALLOCATED

Dear Team/Manci,

Someone please respond to this query very urgently.
I am on a Tier 4 Student Visa and I have been working with an employer for past 5 months. I had applied for a Tier 4 to Tier 2(General) switching 1 month back and got it refused as my HR wrongly put my role under NQF4 instead of NQF6.

Now, my employer has applied for an allocation for me to put a new application since last 2 weeks. My present Visa is expiring on 28th Feb 2015 (few days more), but we haven't heard anything yet from HO. My HR has been constantly e-mailing UKBA and also calling UKBA on the helpline so that the HR can provide me the CoS number for me to apply at the earliest before my present visa expires this week.

Can Manci or anyone please guide me urgently now on what can I do to get my Visa successfully. On worst-case scenario, what can I do if I don't hear anything from UKBA before the 28th Feb 2015? Can I leave the CoS number blank in the application and provide later? Do i need to put a cover letter?

PLEASE HELP

Can someone please assist?