Straighttalk iPhone SIM activation for already Straighttalk activated phone?

It says I need a $45 service plan card to activate the SIM card, but is there a way to do it without? My phone has $45 service plan active right now, my SIM card is just malfunctioning, so I need a new one. Or do I have to do it when I refill, no other option?

Go to Walmart and get a new SIM card, no need to get another $45 plan.