I suspect someone is taking control of my phone. How can I log in to the iCloud account? It's very important to me.
To me it looks like your real issue is not one of too many free accounts but one of a compromised account and/or device.
Read this article if you think your Apple Account has been compromised. --> If you think your Apple Account has been compromised - Apple Support
Use the information in this article to check your Apple ID device list to find where you're signed in --> Review devices signed in to your Apple Account - Apple Support
Related materials:
Personal Safety User Guide
Personal Safety User Guide - Apple Support > open the Table of Contents and review the articles
An article with general information about security and your Apple ID --> Security and your Apple Account - Apple Support
Contact Apple for help with Apple ID account security. This page provides country-specific Apple Support contact information ➞ Contact Apple Support - Apple Support
If a different account is signed into your device you may be able to get Apple to reset the device entirely. Read the requirements and steps for an Activation Lock support request at: https://al-support.apple.com/#/additional-support and links at the bottom right for the type of service requested. Apple says they “may” require "proof of purchase documentation” and that you need “proof of ownership documentation”, but does not detail what currently constitutes proof other than it “must include the product serial number, IMEI or MEID.” User reports on this community and chat with Apple indicate that typically Apple will absolutely require, and ONLY accept, an original receipt issued by Apple or an Apple Authorized Reseller. Presumably this is the only kind Apple can authenticate against fraud since Apple is not involved in third party sales. Apple recommends that you "Keep your receipt after you buy an Apple device" --> Keep your receipt after you buy an Apple device - Apple Support
Note that the device cannot have Lost Mode set on it or is a managed device. If your device has been taken over by you having entered a scammer’s Account then the scammer has likely set Lost Mode and the device is lost to you.
If anybody tells you that you have to be the “original” owner, they are wrong. In the case of removing the lock with the correct information, it can be anybody who knows the currently signed in account information. In the case of asking Apple to unlock it, as long as you have the original Apple receipt (which may well not have any personally identifying information on it) you are okay. Apple confirmed this in a conversation.