Currently, we don't offer prorated upgrades. When you upgrade your plan, your billing cycle resets immediately, and you're charged the full amount for the new plan. The new credit allotment is added to your current balance, giving you more credits to use right away.
If you only need more credits for this month, consider purchasing credit top-ups instead. These can be bought directly from your billing modal without changing your plan or billing cycle. Keep in mind that top-up credits cost 50% more than the typical cost per credit of your existing plan.