Phone calls without answer

I made arrangements this morning with them regarding my personal loan. After that, I have been receiving phone calls from *** or ***. When I answer, the call ends within seconds. Then the calls from Withheld numbers started and again same reaction when I answer. If I decline the call, they phone again as the phone stops ringing. I need the harrassment and calls to stop. I made arrangements exactly for the purpose of avoiding these kinds of calls. I have always been happy with the service received from them, but not today.