Hi LadyTweak,
Welcome to the Support Communities! If the tone that you have chosen for texting is not playing correctly, I would suggest you restart or reset the iPhone first.
Restart or reset your iPhone, iPad, or iPod touch - Apple Support
http://support.apple.com/en-us/HT201559
If that doesn't work, then change the ringtone for texts to a different tone, restart the iPhone and test the new tone; then change the default ringtone for texts back to your pacman song.
iTunes: Using the iTunes Store for iPhone, iPad, and iPod touch - Apple Support
http://support.apple.com/en-us/HT201574
You can't purchase ringtones and alert tones from your computer, but you can purchase them using your iOS device with iOS 5 or later.
To locate tones in iTunes on an iOS device:
- Tap the iTunes Store app.
- Tap Tones. If Tones isn't visible, tap More > Tones.
- Browse for tones. Once you purchase a tone, a dialog appears.
- Choose to set your new tone as your default ringtone or assign it to a contact. If you don't want to do anything with the tone, tap Done.

- Tones you purchase using your iOS device sync to your iTunes library when you connect your device to your computer. You can find tones on your device in Settings > Sounds.
It's possible there is an issue with the pacman tone itself. If so, report the issue to the iTunes Store:
Report a problem with an item purchased from the iTunes Store, App Store, Mac App Store, or iBooks Store - Apple Support
http://support.apple.com/en-us/HT204084
I hope this information helps ....
- Judy