Wow.
Getting in to debt and paying interest when you have a phone that works just fine.
That's smart thinking
!
Not sure if this is what the original poster does but a credit card is much more than that.
With a credit card you can build up a credit rating which is good in future years when you want things like a mortgage. Also they are there for just incase a rainy day comes along.
My current credit card came with 15 months of no interest, a lot of cards come with rewards for spending. Not only that but if you are a victim if fraud with a credit card it is easier and more likely that you will get your money back. This in itself is a perfectly good reason to use a credit card over a debit card.
Also even if you don't have a long no interest period then you still have about a month from the date of purchase to pay it off before accruing interest. Also buying an iPhone on a credit card and paying it off over time whilst having a sim only plan maybe cheaper than the equivalent contract. Also debt it itself isn't bad so long as it's manageable, it's unmanageable debt that is bad.
Lastly, electronic item purchases on credit cards have an extended warranty.