To top up or recharge your Viber account, you can use the Viber out account. If you are short of credit, first open the Viber app and then go to Viber out option.
Here open the Viber world credit, enter the password, and get access to the link where you have to pay the Viber Out fees. Enter the amount of your subscription.
After that, you will get the message that you have recharged your Viber Out account. Make sure that every step you follow with care. You get the subscription you need. You can use the PayPal or credit card to pay the fee for Viber Out.