Potentially. But no.

They *should* only be able to control the SIM.

The handset has an IMEI - the first “i” is International. Essentially there’s a list of lost/stolen phones, identified by their IMEI, and when placed into this list every network supplier is supposed to disallow connection to their services.  So, if they have the IMEI, and have the legal right to assert ownership, they can place the IMEI into this list and neuter it. It’s possible to change the IMEI, but this is unlawful in most countries, and outside the scope of this forum to supply instructions for (which vary by handset). 

More importantly, the question should be:
     Why am I lining myself up for bills I cannot afford to pay?

The answer to that may indicate the legality of what you’re planning to do next. And the downstream consequences you can expect.

Hi @Darren Petrova 

If your bills aren’t paid, we’d block the SIM card and services from it would be restricted.

Any unpaid bills left unpaid over 30 days may affect your credit score, multiple unpaid bills may mean we’ll contact a debt collection agency.

Tom