No, you won't be charged twice if you upgrade your Zendesk plan mid-cycle. Instead, you'll be billed the pro-rated difference for the cost increase of the higher plan for the remainder of the current billing cycle.
This means you only pay for the additional features for the time you use them, rather than paying the full cost of the new plan again. This ensures a fair billing process when you decide to upgrade.
If you upgrade your Zendesk plan in the middle of a billing cycle, you will only be charged the pro-rated difference for the cost increase of the higher plan. This means you'll pay the additional amount for the remainder of the current billing…
When you upgrade your Zendesk plan mid-cycle, the cost is calculated based on the pro-rated difference between your current plan and the new plan. This means you'll only pay for the cost increase for the remaining days in your current billing…