I have upgraded/downgraded my membership and noticed a change in the service fee - how is this possible?

If you have applied for an upgrade/downgrade, you agree to the new conditions that apply as part of the contract change. Your service fee will only change if your old contract includes a service fee. In this case, your membership will be converted to the current conditions so that no service fee will be charged. If you no longer have a service fee in your contract, nothing will change for you.