The credit card details cannot be changed directly on the Ubigi Monthly Plan you benefit from, so you need to cancel it or wait until the registered credit card is expired (the data plan will then be cancelled automatically).
From there, when the validity period of the current renewal has ended, you can subscribe to the same Ubigi Monthly Plan (or another one) and enter your new credit card details during the subscription process.
NB: to avoid a double fee charged for the same period, ensure that you do the new subscription at the end of the current renewal period you benefit from (… and if it happens, you will benefit from a double data plan on that same period 😊).
Your Ubigi Monthly Plan may also appear as “cancelled” or is already no more visible on your Ubigi account before you register your new credit card details. In this case, you can subscribe again to the same Ubigi Monthly Plan and enter your new credit card details during the subscription process. Once validated, your new Ubigi Monthly Plan will start right away.