As you pointed out in your question, the Worker's Compensation Carrier as 21 days to either accept or deny your Worker's Compensation Claim in accordance with Section 406.1 (a) of the Act. If you had provided prompt Notice of your injury to your Employer, the Notice of Temporary Compensation Payable was untimely, and in my opinion invalid. Unfortunately, the Bureau of Worker's Compensation has excepted untimely NTCP's and some Workers Compensation Judges will not Award any Penalties for this Violation of the Act.
With respect to your Employer controlling your medical treatment, in order to do so they must not only have a List of Designated Physicians posted at a readily accessible place at your worksite, but also must secure your signature upon the Required Notice of Employee Rights and Duties at or about the time that you reported your injury to your Employer. In the event that they do not do both you are not required to treat with physicians of your Employer's Choosing. If, however, your Employer to comply with its obligations pursuant to the Medical Containment Regulations and the "panel position" recommend surgery within the initial 90 days of Employer Controlled Medical Treatment, you are entitled to secure a "2nd opinion" regarding alternative treatment options and continued to treat with the physician who recommended surgery for an additional 90 days utilizing either the recommended procedure and/or the alternative treatment recommended by the "2nd opinion."