/**
 * Sets the phone number of the user.
 *
 * @param phoneNumber - Must be no more than 255 characters in length and
 *   contain only numbers, whitespace, and the following special characters +.-() Accepts an explicit null value to
 *   unset the phone number.
 *
 * @returns Resolves to a boolean that indicates whether the update was successfully enqueued. Resolves to undefined
 *   if the SDK is not initialized.
 */
export declare function setUserPhoneNumber(phoneNumber: string | null): Promise<boolean | undefined>;