If It's plainly not allowing you to switch now or for the next cycle I'd contact the Moderator Team. Here's how.
Need assistance with your account, activation, or service?
In your private message please include the following:
Don't know your PIN? Provide any three of the following:
When will they get back to you?:
Also you can edit your post via the 3 dots on the top right of your post if you make a mistake btw.
You can future date a plan change to happen on your next renewal. If topped up in last couple days you could ask mods politely and to change you to cheaper plan and credit you the difference you may/may not have success in this.
Also if a plan is expired the system does not let you change plans only renew the current plsn
well you have to go to your profile and edit your plan there.its says CHANGE PLAN click on there and you can change.i also saw better to change went one is finish..i see you topped your account so you should be good..