LastPass Support has no knowledge of a user's master password. It is not possible for LastPass Support to reset or change a user's master password if it is forgotten.

All encryption and decryption occurs locally on the user’s device, not on our servers. This means that your sensitive data does not travel over the Internet and never touches our servers. Your data is only transmitted to LastPass once it is encrypted. We don’t have access to your sensitive data, nor could anyone who potentially abuses our systems get access to it. We have zero knowledge of your confidential information, including your master password. For this reason, LastPass Support does not have the ability to reset your master password if it is ever lost or forgotten.

For more information, please see How is LastPass safe? and Since my LastPass vault is encrypted with my master password, why can my One Time Passwords decrypt it?