@selva1 the bonus data is associated with the account, not your base plan. This is no different with any other add-on such as long distance minutes or US roaming. These are add-ons and will only go away once you've used them up (or in the US roaming case when the 10 days are up). So definitely feel comfortable doing the plan change without worrying about losing anything.
Same goes for the refer a friend reward. This reward is associated with your account, not your base plan. So you can make as many changes as you want on your account, this reward will always remain (unless the person you referred changes to another cell company).
