The number customers have been calling for ten years belongs to you, not to your operator. You can switch provider and keep it, but the procedure has strict rules and one dangerous spot: a landline number bundled into a fibre offer.
The number is yours: what the law says
Portability is a right of the subscriber, not a favour from the operator: the number stays assigned to you when you switch provider, and the Italian electronic communications code keeps it available for at least a month after the contract ends.
The request always goes to the new operator, never to the one you are leaving: the receiving operator opens the procedure and sends the termination notice. Cancel on your own first and the number drops back into the old operator's pool, where getting it back is close to hopeless.
Mobile: what you need and how many days it takes
A mobile number needs three things: the ICCID of the SIM (the 19 digits printed on the card or shown in your phone settings), the holder's details with the tax code or VAT number, and valid ID. No secret code, no call to the operator you are leaving.
You sign with the new operator, get the SIM and activate it: the switch usually completes in one to three working days. The line goes quiet for a few minutes during the swap, almost always overnight. Book it for the start of the week, not for a Friday.
Landline: the migration code and the real timescales
A fixed line needs the migration code, an alphanumeric string printed on the bill or shown in the customer area of the operator you are leaving. You also need the exact address of the line and the holder's name written exactly as on the contract: a shop sign instead of the registered company name gets the request rejected.
Timescales run longer than on mobile: from ten working days upwards when only the operator changes, longer when the technology changes too, copper to fibre for instance. Keep the old line alive until the new one carries a call.
The number tied to fibre: where it gets lost
In most fibre offers the landline number is a VoIP service inside the bundle. Moving it to another operator closes the voice part in practice, and some contracts treat that as a partial termination: the promotional discount falls away, or the instalments on the router become due.
Before you file anything, ask the operator in writing what happens to the connection and to the price if only the number leaves. If the answer stays vague, leave the number where it is and send the calls elsewhere with call forwarding.
Costs, lock-ins and penalties
The transfer itself is free and cannot be invoiced. What can be charged are exit costs, which by law must be proportionate to what the operator actually spends and must be stated before you sign, plus the remaining instalments on a phone or a router taken on subscription.
Notice of termination cannot exceed thirty days. If a generic penalty shows up on the closing bill without being described in the economic conditions, dispute it: first with the operator, then through a free conciliation at the Corecom.
What to check before you switch
Check five points: who the number is registered to (if it is still the previous owner of the business, transfer the contract first), whether the geographic number stays inside its own dialling district, the minimum term, the exit costs written in euros, and what becomes of the rest of the bundle.
A geographic number only moves inside its own numbering area: take the business to another province and the old area code will not follow. Then one route is left, keeping the historic line and forwarding its calls to the new number.
With Rispondly nothing has to be transferred: the number stays yours, you set up a forward and the assistant answers on it.