My purchased ringtone is not playing on my iPhone

Re: why when i bought the ring tone for my phone it was not playing when my phone rang

Seems the ringtone you hear depends on which ringtone you have set to play in your settings.

Purchasing the ringtone would likely add it to your list of ringtones, yet It is up to you just where you use it.

(Eg: You may have wanted to assign it to calls from a certain person, or just to all calls.)

See Apple support's online article: How to: Use tones and ringtones with your iPhone or iPad - Apple Support

Eg: says: "Change your ringtone

1. Go to Settings > Sounds & Haptics.
2. Tap the sound you want to change.
3. Tap a ringtone or alert tone to hear it and set it as the new sound."

or

"Set a ringtone or text tone for a contact

1. Open the Contacts app and tap a person's name.
2. In the top right-hand corner of the person's contact card, tap Edit.
3. Tap Ringtone or Text Tone, then choose a new sound."