Check what the charges are for. The purchase history for your account will specify that precisely. A lot of items are 4.99, so the amount by itself doesn’t mean anything.
If you see 'apple.com/bill' on your billing statement - Apple Support
See your purchase history for the App Store, iTunes Store, and more - Apple Support
Check your subscriptions. The subscriptions overview page will tell you the next billing date for each subscription.
Check your subscription confirmation email. It will tell you what the duration of the free trial period was initially.
Verify that you haven’t canceled and then re-subscribed, as that would end the free trial and begin the subscription fees.
What is this “we”? Apple ID accounts are individual. Did both of you each redeem the offer? Did both of you get charged unexpectedly?