How Can I Get My Desired Job!

Fellow Nairalanders,
I have a similar problem, am a 2.2 B.Sc degree holder in Bus.Admin.,
with professional certificate; ACMA, ACRM,CCNA respectivefully,But i have strong passion for Computer Networking
which lead me to wrote the Cisco Exam-CCNA which i successfully passed Last year.Now am working as a Network Administrator but the workload is too tedious and i barely have time for myself to do other things.
The most painful part is that i have been applying for Computer Networking jobs but am yet to receive reply or invitation
for interview.For the few ones have attend they want to employ me as a marketer which i don't have interest.
How can i work in one of these big companies as a Computer person regardless of my first Degree.
Please advise!!!

@ gabrywyl yes u said it all
@poster your first degree doesnt matter much, its your passion towards the area that matters the most.
 one of the ED's of Systemspecs read physics as first degree