Re: how can I block unwanted cals and textsr from my iPhone 5
You can MUTE them so that you still receive their texts but don't get a notification. That's good for receipts, and also good if this is serious and you need proof of stalking in the future. You can mute them by clicking on the convo in Messages, going to details (top right), and turning on Do Not Disturb.
To BLOCK, go to Phone, go to Recent, go to the number that's bothering you, click on Info (the blue i next to the number), scroll all the way to the bottom and click Block This Caller, and click the red Block This Caller to confirm. This works if it's a number that you don't recognize.
You can also BLOCK through Settings, Phone, Blocked, Add New. Then you add who you want to block (this is if you know who it is / the person is in your contacts list).
Also, if this is real stalking, go to the police. Be safe, and good luck!