Then put the phone in airplane mode (make sure you have a password program on your phone first - I use
KeePassDroid - it's as good as the paid ones if you use Google Drive as the cloud for it). Go to a PC and
change the password on every single account you have online! You can use
KeePass on the PC to generate
at least 20 character mixed upper/lower case alpha. numeric and special character passwords. A different one for each account.
This includes your Google account! Then close the program.
Rename the kdbx file it generates so no one looking at it would guess that it's a passsword file (not that anyone can get into your Google accounts), then copy it to your Drive account. Open the program again and open the file on your Drive folder. (You'll probably have to relogin to your Google account, so when KeePass makes the password for it, write it down somewhere.)
Now turn off airplane mode in the phone, open Drive, go to the kdbx file and share it to the phone. (If you have to relogin to your Google account, you have the password written down.) Now run KeePassDroid, open the kdbx file, and you can use the passwords in there to open all your accounts as you get to them.
If all the person is doing is calling you and texting you, you can take the police report (as belodion suggested - go to them and report this stalking) to your carrier and have your number changed. Then go to
Google Voice, get yourself a Google Voice number and forward voice and text to your new number. Which one you give out as your number is up to you (I use my GV number, so I never have to worry about porting again - if I get a new number, I just forward the GV number to my new number.)
Give the new number out to one person at a time, and wait a day or so before giving it to the next person. If the calls/texts start again, you'll know where the stalker got the new number. (The friend may not be the stalker, but someone may have said to him or her, "You know, I can't seem to get X on the phone any more", and the friend gave them your new number. But give that information to the police too.
