Totally understand the concern there, especially since you're already paying for your cellphone.
I did something similar a couple years ago when we were shopping for a car. A lot of car shopping sites are basically lead generators for dealerships and you need to provide a number to get real info. I used a Twilio number forwarded to my cellphone.
The deluge of calls started immediately. After 48 hours, when we had all the information we needed, I released the Twilio number and incurred no further charges.
Total cost was $1 (per month) for the phone number and $0.01 per minute for the inbound calls. Upside was that my phone stopped ringing the moment I was done talking to salesmen.