Monopolies are not a yes or no thing. Since Apple has a large enough market share that it is able to strangle competitors just through having that kind of market share, it is having a monopolistic effect on various markets.

For example, the smartphone market, if the smartphone market was perfectly competitive, if I didn't like Apple's and Google's business, I would be able to go to a third seller and get similar products. If I didn't like them, I could go to a fourth, and so on until it becomes meaningless. Like the market for actual apples for example.

Since that is not true, Apple is distorting the smartphone market with its large market share, making it have monopolistic tendencies.