Have no fear frustrated user. No need to smash your old phone or tools. There's not even a need to buy a new phone!
So, you didn't mention which screws are stripped, but you have a few options for removal depending on accessibility of the screws.
1: Drill em out. Use a bit just a tiny bit wider than the screw body (use other screws as a judgement) and drill the head off. This method is typically high vibration and generally vary rough on your gear.
2: Slot the screws with a dremel cutting bit, then use a flat head to extract. Again the cutting can be rough on the phone and this option may not be plausible depending on screw location.
3: Screw extractor set. Much nicer on your equipment and may come in handy for future applications? May not work if you've completely rounded the heads out.
4: Screw extracting pliers. May not be usable if there isn't sufficient clearance around your targeted screws but is another gentler alternative to dremeling and drilling.
Any of these methods will work. Naturally the use of power tools requires extra caution to prevent collateral damage to the phone and yourself. Choose your weapon and good luck!