Once your account get suspended then you won't be able to switch plan that's how system work.
Your account need to be active while switching plans also valid plan have a future date option means you can manually pick a plan and setup feature date according to your renewal date. But since your account suspended only way for you to switch is first you need to top up your account for old plan then switch and lay again but you will be paying double. That's why we highly recommend once accout suspended contact mod member if you looking to switch plan. So they can manually fix it for you.
Also for your reference if in future you want to switch you can either switch one day before your renewal date or preset the future date so this way your account won't get suspended or double charge.
For now your only option is to contact mod and provide basic details like name email and number along details explanation and you will find link on earlier post
Thanks
** I am not a Mod, please do not include any private info in a private message to me.**