If your plane is a high wing configuration and the nose pitches up with an increased throttle, it is a thrust vector problem as Zeeb stated. Every high wing plane I’ve had either does this or would if the engine weren’t angled down. If the airplane climbs because the lift increases as the speed increases, that is what airplanes suppose to do.
Yes, you could set up a program mix to add down elevator as the throttle increase. But you have to be extremely careful in not having too much down-elevator mix. I’ve done this on my electric powered sailplanes where it wasn’t possible to alter the thrust line. It is very disconcerting to launch a plane and it dives to the ground when giving it power and drops to the ground when letting up on the throttle.
Allan