I have a Google Pixel 2 XL and last week I moved from Vodafone to Spark.
I routinely use data/mobile hotspot while on a phone call. For some reason, since moving to Spark the data performance while on a call is terrible/unusable. Once the call is terminated it is very responsive/fast.
I am in the Eastern Bay of Plenty, in town center with 4G.
What could the cause of this be? I'm sure it can't be a spark thing, as surely nobody would use them. But I didn't have the problem with Vodafone a week ago so...? (hence posting here)
I don't have another phone readily available for testing but that or factory reset would be my next troubleshooting step.