What happens if I don't make the first payment phone contract?

I took out contract on Vodafone for Iphone 7. Haven't made first payment and my sim has been restricted. Can only get incoming calls. What happens if I don't pay

A friend said if I make no payments i'm not tied in the contract

Your friend is wrong.

Your friend is an idiot.

A contract is a legally binding agreement. Don't pay and you could have your credit trashed, be sued, have your wages garnished, etc.

If you make no payments you have voided the contract and they don't have to even allow incoming calls.

You will lose your service entirely and your credit rating will drop.

Pay up.

The phone would be blacklisted.

Your friend doesn't have a clue. Your obligation to fulfill your contract is effective from the time you sign the agreement, NOT when you make the first payment. Don't take any more advice from this person.

Your friend is wrong.

After about 15 days, the phone will be blacklisted and you will have no service.

The phone is useless until you are current on your payment.

Vodafone will add fees and interest to the unpaid balance, possibly doubling what you owe.

You will be taken to court and a CCJ will be issued and likely escalates to the High Court. Expect bailiffs at your door to collect the full contract amount plus fees. Can't or won't pay? The bailiffs will seize goods.

Your credit will take a large hit.

You won't be able to get a phone under contract without a significant deposit for at least 10 years.

If you have significant debts in default, your ability to travel outside the EU may be hampered.

You screw up your credit for at least 7 years is my best guess. Possibly going to small claims court and being hounded by collection agencies.
Your friend may have been thinking if you return your phone during the Trail Period you will still pay money like a restocking fee and the first months bill bull after you return the phone and pay those charges you will not have a contract but you likely already exceed your trial period if you got first bill.

If you do not make any payments as set out in the plan, then you will be charged an early cancellation fee, which will cost you more than total amount payable under the contract, and the phone number will be disconnected permanently

You can (and this is an immoral and unethical thing to do when it can be avoided) is get a prepaid sim with another carrier and port your number to it.