It depends on your usage and needs.
Buying Phoner number via a subscription:
If you plan to use the product for a long period of time, a subscription may be more cost-effective. In addition, your Phoner number will automatically renewed, ensuring that you are connected to your contacts all the time.
Buying Phoner number via a one-time Credit purchase:
If you only need to use the product once or infrequently, a one-time purchase may be more suitable. Consider your budget and usage habits when making a decision.