CVT going haywire?

[kat4a]

Just had my oil changed and tires rotated last week and since then particularly when I'm on the highway the CVT seems to be going haywire - the RPM are all over the place, especially when accelerating but also sometimes when maintaining speed. They keep jumping up and down but mostly stay in the low end. If accelerating to enter the highway, for example, instead of the RPM getting up a bit higher like usual, they jump around from 200-250 or 300 and the car does not accelerate effectively.

Any ideas? Problem with the CVT? Something they did during the tune up? (Was done at the Nissan deanship, BTW) Thanks!