Google has updated play store version to 3.7.15   removing some bugs which were in 3.7.13, Play Store 3.7.15 is just a modification to 3.7.13, improvising the stability and bugs removal. But in Google play store 3.7.15  there is an error like “Error purchasing df-bpa-09″.

HOW TO FIX:

Instructions: 

Go to settings>applications>play store, and clear the data.

If this doesn’t help you try this

Go to settings>accounts & sync> Google, Unsync Gmail,  Resync Gmail.

Doing this it will fix the ”error purchasing df-bpa-09″ error.