You can find out about our pricing here.
Yes, you can edit collaborator emails at any time in Account settings. Changes become effective the moment you save them and have no effect billing-wise as long as the number of collaborators stays the same.
If you increase the number of collaborators, you will be billed based on the time left in the current billing cycle. For example, if you pay monthly and you add 10 users in the very beginning of the billing cycle, you'll be charged 10 x $4 = $40, but if you do the same in the middle of the cycle, you will only be charged half of that amount, that is $20. This proration is made with precision down to the second. The fee is either charged immediately or added to the next recurring subscription charge, depending on the amount.
If you decrease the number of collaborators by X, you will not be refunded the part of the fee that covers those X people using the service for remainder of the current billing cycle, but that amount will be credited to your Obvibase account and automatically taken out of future charges. For example, if you start a monthly billing cycle with 14 users, then in the middle of the month decrease the number of users to 10, that will mean that you initially 'overpaid' for 4 collaborators using the service for half a month, 4 x $4 / 2 = $8. That $8 will be credited to your account, and in the beginning of the next month you will be charged $32 instead of $40.
Yes, you can do this at any time. The new billing cycle will start from the date of the switch. You will not be refunded the part of the fee that covers the remaining part of the old billing cycle, but that amount will be credited to your account and taken out of future charges. If for example you have 2 users on a yearly plan (2 x 12 x $3 = $72/year) and switch to monthly two thirds into the billing year, the $72 / 3 = $24 that covers the remaining third of the year will be credited to your account. For the first three months, instead of being charged $8/month, you will not be charged anything, instead the fee will be taken out of your credit, and then once the credit runs out you will begin to be charged normally.
We never store any sensitive credit card data on our servers and let our payment processor, Stripe, handle payments and keep credit card data secure. Stripe has been audited by a PCI-certified auditor, and is certified to PCI Service Provider Level 1, the most stringent level of certification available.