Aboneliği iptal etmek istiyorum.

I want to cancel the subscription.

Breakdown of Aboneliği iptal etmek istiyorum.

• istemek: to want
• abonelik: the subscription
• iptal etmek: to cancel

Questions & Answers about Aboneliği iptal etmek istiyorum.

Why does aboneliği have an –i suffix? Is that showing possession?

No – that final –i is the accusative (direct-object) marker, not a possessive. In Turkish, when a definite object (something specific) follows a verb, you usually add –i / –ı / –u / –ü (according to vowel harmony) to mark it.
• Root noun: abonelik (“subscription”)
• + accusative: aboneliği (“the subscription” as the object)

A true “my subscription” would be aboneliğim, where –im is the 1st-person possessive.

Why isn’t there a –im (“my”) on abonelik? How would I say “I want to cancel my subscription”?

You can absolutely specify “my” if you like:
Aboneliğimi iptal etmek istiyorum.
Here:
• abonelik = subscription
• –im = my
• –i = accusative

When you omit –im, Turkish assumes you mean the subscription relevant to the conversation (often your own). Dropping the possessive is common in headings or short service requests.

What role does etmek play in iptal etmek? Isn’t iptal already “to cancel”?