I am receiving unwanted phone calls at 2.30 every night

Nice to meet you, *****!
And which phone do you get the calls on?

What's the model and brand?

Are you on the phone right now?

Try doing this:

1. At the very beginning open Settings.
2. Next move to the Sound section.
3. Tap on Do Not Disturb
4. Choose Turn On Automatically
5. Select Add Rule
6. Click on Time
7. Add Time Rule and tap on Add button
8. To confirm the whole process click on Switcher to Switch On this Rule

Nope, you can choose set time:)

I'm afraid it's impossible to know that, however, you could call your carrier
What's your carrier?

Most likely
Try calling this number 0344 8090222

This one should be free +44 7860 980 202