A free trial or a heavily discounted first period is one of the most common ways subscription and membership services attract new customers, and the offer itself is often exactly as described. What causes the most frustration is not the trial period, but what is scheduled to happen automatically once it ends, particularly when the signup was originally made for a short, specific need rather than an ongoing one.
Most trial and introductory-price offers are set up to convert automatically into a standard-priced, recurring membership unless the account holder actively cancels beforehand. This structure is disclosed in the terms, but it is rarely the most visible part of the offer, since the discounted or free headline price is what draws attention on the signup page itself. Some services also increase the renewal price gradually after the first standard-priced term, which is worth checking separately from the initial trial conversion.
A small amount of checking at signup avoids most of the unwanted charges that come from this structure later.
Setting a reminder a few days before the conversion date, rather than on the date itself, allows time to decide deliberately whether the ongoing subscription is worth its standard price, instead of reacting to a charge that has already gone through. This is particularly useful for services signed up for around a specific need, since the underlying reason for joining may no longer apply once the discounted period ends.
Trial and introductory membership offers are not inherently poor value, and many people continue a subscription happily past the discounted period. The habit that protects against an unwanted ongoing charge is simply treating the renewal date as the moment that matters most, and deciding about it in advance rather than being reminded of it by a bill.