Both H1 and H4 approved. What to do next?

I am currently on H4 visa. As it was expiring on 30th Sept 2014, My spouse’s company applied for an extension. In the mean while another employer applied for my H1 visa (with COS) which got approved on 21st July 2014 while H4 got approved on 5 Aug 2014.

What should be done now to ensure I remain on H1 Visa? Does last action rule holds significance in my case?

Any advice in this will be really helpful.