Jerold Kaplan Law Office Can't contact company goes straight to voicemail. Phoenix, Arizona

 I have been paying company for over two years, I have never been late.  I started calling company before my bill was due, like  I usually do.  I started calling on the 17th of Jan., my bill is due on the 22nd.  They always take payment over the phone. 

Since the 17th, I have been calling two to three times a day and keep getting a recording.  So I leave my information for somone to call me back. No one answers or returns calls.  Now on the 26th, I get letter in mail stating I am late and it is urgrent to get a hold of someone, but how is that possible.  At a loss of what to do.

I am going to send check certified mail and put it to the attention to the person they said.  How can a company call you late when they themselves do not answer or return calls.