discuss together. you can’t just drop a bomb declaring that you are changing the current arrangements without some discussion, input and planning from your child. set up a time to talk. don’t shock them with a big announcement, because you will likely incite a revolt instead of trying to work co-operatively towards a solution that suits you both.
set a budget, but allow some time before beginning. decide what you will and won’t pay for as well as a reasonable “stop date” for the items you are not willing to cover anymore so your child has time to prepare for losing those funds. it’s an easier and more respectful transition, for example, when you say, “you’re a graduate, you’re in the workforce, your allowance will be ending after three months.”
keep it open-ended. remind your child that this is the first iteration of the new agreement and if they go back to school, get laid off at work, or some other situation arises, the agreement can be revisited. you are a flexible and reasonable person — you are not trying to cause hardship. this is about the child accepting their responsibilities as a young adult.
trust your gut. if you are feeling resentment, then you are paying for something you don’t think is reasonable. also, make sure you don’t tie your willingness to support your child with certain behaviours. “i pay for your wifi because it’s my responsibility as a parent to cover the basics,” is very different than, “i can’t believe you are so rude to me and i am paying for your phone — i am cutting it off until you treat me better.”