i got email saying that someone in purto rico tried to sign in to my account. changed password now phone jingles every twenty seconds with login failure

i would like to know if this happens often or if it is a hoax.  I need to know how to get my phone from jingling every 20 seconds with failed attempts at log ins (I am not logging in.) or is my phone trying to auto log in .  I do not know what is going on or what to do about it.   Thanks for any help