Am I in the wrong?

Yes and no. Yes if you where ordering something taboo, like porn or whatever. I would have waited till his permission. If it was for medication or food then still yes, but could be understood.

It is good to hash things out and was a learning experience. Life with roommates is a learning experience, and you can discuss it with your roommate for next time that something like this happens again what to do..

Looks like you might need to discuss what is and isn’t cool in the future. We all make mistakes and best we can do is learn from them.

Yes, you were in the wrong. Don’t use people’s info without their direct permission.

Why was your number no good? That would be a red flag for your roommate that you should never be allowed to use his number. You are irresponsible.

Yes, you’re in the wrong. Even if you ordered something as mundane as pizza, it’s really not okay to use someone else’s number without their permission.

Asking—but not waiting for their answer—does not actually count as asking for permission.

“Also, he can see I asked first before putting it down…”
– And then, without receiving permission, you did it anyway. And now you’re still being defensive about it.

Yes, you are in the wrong. His number is his, and using it without his permission in any way is a violation of his boundaries. All people, but roommates in particular, deserve healthy boundaries, and violating them is messing with them and makes people rightly wonder whether or not you can be trusted in all things. Your thinking here demonstrates that you aren’t sensitive to that sort of thing, and that you may self-justify/rationalize unilateral actions and do things without consent, and then argue about it.

Realize this, apologize, explain to the roommate that you understand it was wrong and promise not to do that sort of thing again, and then don’t do that sort of thing again.

Yes you were in the wrong. Just because you would be ok with something, doesn’t mean THEY would be ok with it. Apologize sincerely and move on. It was a mistake, but not one worth losing a friendship over.

It doesn’t matter if it wouldn’t have bothered you, not everyone is going to feel as you do. It doesn’t matter that you tried to ask and can prove it, not everyone is going to think that is OK.
Yes, you are in the wrong, and no, he is not overreacting. You owe him a sincere (not annoyed and cursory) apology, without excuses, and with honest remorse. No “but no harm was done!” and no “but I wouldn’t have minded had you done this”. Just an honest apology, and an assurance that it won’t happen again.

I think you are, yes. You’ve shown your housemate in big red capital letters that you are not to be trusted. I’d say apologize again, damn quick, admitting you WERE in the wrong, and never do it again.

We’re talking about a phone numbere, right? Or was it some other number?

Yes, you are in the wrong. Using anyone else’s PII (Personal Identifiable Information) data elements is out of bounds.
Let me put it in a different perspective.
Companies fire people and get penalized if they give out any Personal Identifiable Information.
You have lost an element of trust similar to a company loosing your element of trust in them if they gave out your PII.

Follow-up question: Have you paid him back?

You should have venmo’d him the amount you charged immediatey after hitting send..

@zenvelo I don’t think OP used their roommate’s credit card information or charged anything.

Years ago I loaned a friend a VHS I recorded of a movie. It was on a cassette labeled “Junk Tape”. My friend asked if I had the movie, and I loaned it to him. He watched it, then recorded over it, figuring it was a junk tape, and I was done with it. He didn’t ask, and I hadn’t actually watched the movie yet.
He didn’t see the big deal about it, because it was clearly labeled as Junk. My feelings were hurt because he presumed it was okay to do this without asking.
Okay, that was like 40 years ago, but I still have a small twinge when I think about it.
I am sure he hasn’t thought about it in 40 years.

Boundaries, boundaries. How many problems come down to respecting or violating boundaries, between two little people in the anthill on up to entire countries. When people think about this, they usually talk about their own boundaries, but what’s the point unless we also watch out for other people’s boundaries? And don’t assume necessarily they’re the same as ours.

@raum He was “doing an online order”. If he wasn’t using his credit card, what number would he have been using?

I think he owes his roommate money.

@zenvelo: ”…not like I have used his credit information to buy it without his permission.”

@zenvelo I’m guessing OP meant phone number?

I think they owe their roommate a genuine apology (without excuses or being defensive).

Yeppers. You are wrong.

My own mother doesn’t use my credit card or personal info without asking me first. Or my husband.

Just so you know it is a crime here, as well. Better make it right with him quickly.

I thought it was phone number like for ordering take-out. But maybe better let OP clarify instead of trying to solve it by debate.

I’d like to know what this part means, though: “my number was being flagged up as already in use.”

Regardless, OP had no business using anyone’s number other than his own.

Shit happens, we all make mistakes. Hopefully this will blow over. Call it a life lesson and try not to do it again.