Are you local or foreigner. I am a filipina i also have same experince as you but the nos start from 6703305061, 62, 63,64 65. I complained to my provide M1. They informed me it came from a machine but they cannot give specifications. M1 is giving the option to change no but I can"t change my number from time to time as I am using this for my official business. People will lost confidence if you change no. from time to time just because of nuisance calls like this.
me and my wife have the same problem as Mariel since a week.
The nos start from 6703305061, 62, 63,64 65. I complained to Starhub today but they tell me they cannot do anything. They cannot block the numbers. I was told to log a case with the Police !!! so they will start an investigation. When I called the police they asked me to log a complaint at any office and not over the phone.
I've been getting these calls too, startingd last Wednesday. I am in the same position as Mariel, I run a business and can't change my number so easily. Even if I did, the problem may return because it seems hundreds, maybe thousands, of people in Singapore & Malaysia are having the same problem.