They call before XXXX XXXX and frequently during a day without leaving any messages. I asked several times to not call me but it did not work. 
They claim that they are debt collector but their information is wrong. When called back operator asked me for my personal information ; I hang up without disclosing anything. 
Their numer on caller ID is ( XXXX ) XXXX, and the displayed name is " Maryland ''. 
Automated voice does not pronounce company name clearly enough : " ... World system Incorporated ''.