I did an Asurion Phone Claim - had S4 they gave me an S5 Active; SIM upgrade prob

First time posting for help so please forgive me for any errors in etiquette...

History:

My Samsung Galaxy S4's charging port finally gave out. So, I had to make a phone claim with the insurance offered by AT&T thru Asurion. I assumed they would send me another S4. Surprisingly, they sent me a Samsung Galaxy S5 Active. I love free upgrades as much as the next person so no complaints there.

Along witht the S5 Active they also sent me and new SIM. However there were no instructions included in the packaging on what to do with this new SIM card.

So I tried just putting it in....and no connection to the network. No prompts to register new device,etc.

Then I put in my old SIM from my S4 and I got on the network. I thought oh good that's all I needed to do. I sent in my broken phone and thought all was well UNTIL....

Current Problem:

The S5 Active download speeds and connectivity seems MUCH slower than with my old S4. Also, some of the apps (Soft Card, etc) do not work unless I upgrade the SIM. 

So my assumption is that I need somehow utilize this new SIM card that was sent with the S5 Active. Am I right in thinking this?

If so, how do I do that? and to create further drama - I don't have a 2nd phone/device, landline, to utilize. Is there a way to do this online or without needing a 2nd phone?

No secondary phone line (not for 4 days when I have family over). Ugh!

Thank you for reading this and attempting to help. I genuinely appreciate it!