Q: how do i delete my icloud account

That isn't being caused by your iCloud account.  It's because your phone number is still registered on Apple's iMessage server because you didn't turn off iMessage on your iPhone.

There are two things you can try.  If you registered your device with Apple using a support profile, try going to https://supportprofile.apple.com/MySupportProfile.do and unregistering it.  Also, change the password associated with the Apple ID that you were using for iMessage by going to https://iforgot.apple.com.

If neither of these work, you'll have to contact Apple support for assistance.

Going to Support Profile only unregisters the device from the user for warranty information, but not for iMessage.

This article covers this topic specifically: http://support.apple.com/kb/ts5185

Symptoms

If you experience any of these symptoms, you may want to deactivate iMessage:

• You can't receive SMS on your non-Apple device when another person sends them using an iPhone.
• You can't send SMS to a non-Apple device because they send as an iMessage.

Resolution

If you experienced the symptoms above, your cellular phone number may still be registered with iMessage. When you turn iMessage on with your iPhone, iMessage registers your cellular telephone number.

To deregister your phone number, tap Settings > Messages and turn iMessage off.

If you can't deactivate iMessage after you perform the steps above or you can't access the iPhone, please contact Apple Support.

Jay-Ray wrote:

 

Going to Support Profile only unregisters the device form the user for warranty information, but not for iMessage.

 

That isn't correct.  It also can unregister a device for iMessage, as can resetting the Apple ID password, as documented in "Note" under "Additional Information: Unlink a phone number" here: http://support.apple.com/kb/HT5538.

Please re-read this document as there are no direction guiding someone to supportprofile.apple.com

I have pasted a copy of your referenced section for your review:

Additional Information

Unlink a phone number

To remove a phone number from an Apple ID, sign out of FaceTime and Messages on your iPhone:

• Settings > Messages > Send & Receive. Tap your Apple ID, then tap Sign Out.
• Settings > FaceTime. Tap your Apple ID, then tap Sign Out.

This should remove your phone number from other devices using the same Apple ID with FaceTime and Messages. If the phone number is still available on other devices after you sign out of FaceTime and iMessage on the iPhone, you may need to sign out of iMessage and FaceTime on all your devices, then sign in to FaceTime and Messages again on devices you want to use.

Note: If you no longer have access to the iPhone that is using the number you want to remove, reset your Apple IDpassword.

Removing from the support profile isn't documented there, the reference to resetting the password is.  Removing from the support profile isn't documented, but has worked in the past for many users.  Apple no longer uses support profiles so has removed this from it's documentation.