Hi, I'm so sorry you've had this experience, this sw sounds grossly unprofessional. You can report to the HCPC which is the regulatory body for all social workers in England. Also, if the sw is employed by the local authority you should be able to phone up and make a complaint. Telling you you'd be known as the complainer to discourage you from making a complaint is disgraceful.
A lot of social workers are overworked yes, however that doesn't help you much. As sad as it is I find that those who shout the loudest have a better result, so keep on at them. They do have a duty of care.
Good luck