Kant says it is always wrong, do you agree or disagree? Is it always wrong to use other people for one's own purpose?
Kant did not say that it is wrong to view someone as a means. He said it is wrong to view someone as only a means.
When a farmer gets a laborer to collects crops, he is using another person as a means to further his own ends. If this farmer pays this laborer money, he is helping the laborer reach their own ends, which requires acknowledging that this other person desires their own ends. Therefor, the farmer is acting morally.
What is important to Kant is the acknowledgment of the other's ends, not in helping the other further their ends. If the laborer was a friend of the farmer and did this work without compensation, the farmer would have still acted morally since being friends with the laborer also requires acknowledging that they have their own ends. Both hiring someone to do work and having a friend do work without compensation are ways to use people as means without denying that they have their own ends.
In contrast, if the laborer were a slave, then the farmer would not be acknowledging that the laborer has their own ends. To the slave-owner, a slave is only a means to which further their own ends and do not themselves desire ends. Therefor, slavery is immoral.
Apply Kant's categorical imperative, and try to assert this as a universal rule. Under what conditions would you consider it acceptable to be used by someone else for their purposes? There are cases where we might choose to do this (for our own purposes), but it's clear we would resent any compulsion, coercion, deceit, or similarly nefarious means of getting us to achieve someone else's ends. We would not will that for ourselves, our loved ones, or our friends; thus we cannot will it as a universal rule; thus it is intrinsically (rationally) immoral.
If one's own purpose is to help others, would you consider it wrong to use them to achieve it ? It is all a question of perspective and serving one's own purpose does not always mean contributing to a single purpose that will only be useful to one human being and as such can always be considered wrong. However, this only applies in the case if we consider "wrongness" to be related to the usefulness of something, i.e., if it is useful for a single person or an actual community.