Will I be charged for out-of-bundle minutes?

Onoff is a secondary line system, which works using your main line's SIM card or your Internet/Wifi network.
Your Onoff number being directly linked to the sim card installed on the mobile used, your communications sent will therefore be deducted from your plan under the same conditions as those of your native number. If you have an unlimited call plan, then your communications from your Onoff number will also be unlimited. If your operator charges for calls to or from abroad, the same will apply to Onoff communications which will transit to or from your SIM card.
You have the possibility to make and receive your calls only in VOIP provided that the country where the call is made or received, does not block VOIP