Yes, that is permitted if necessary. For example, to improve telephone services in a call centre. You do have the right to know if your calls are being recorded. Your employer also has to comply with the conditions of privacy legislation, the GDPR.
Continuous recording of your telephone calls is only permitted if this is necessary for the provision of services, such as with telephone stock exchange orders. In that case, your employer may only use the recordings as proof of the concluded contract.
Read more: Recording telephone calls