OK, so it's been a little while since coming back to this thread.
A network change was done to Activate this on spark's network.
Calling between my vf and spark sim, personally i say the spark service is alot more responsive.
VF
Spark
The key details i pick through is, Spark was lower latency thus feeling more responsive and Spark Scaled up downstream WAY faster.
I understand OP has switched back, but figured i'd close out the thread with saying. The issue was heard, it was resolved and is working well.
I'm still surprised this is even a thing... news to me, i always thought 3G call meant no data GG.