Get list of service levels

<Info icon="fa-light fa-lock-open" className="permission-callout"> <div className="permission-callout__header"><span className="permission-callout__title"><span className="permission-callout__label">Required permissions</span> <span className="fern-docs-badge small blue subtle rounded-full permission-callout__beta">Beta</span></span> <span className="permission-callout__learn-more">[Learn more](/developers/api-guidelines/permissions#how-permissions-work)</span></div> No permission required. Available to all roles. </Info> Returns a list of service levels that can be configured on a tariff plan level. For non-enterprise organisations, only own service levels will be returned. For enterprise organisations, only the service levels of the parent organisation will be returned.