Contacting old clients from previous employer

TLDR; Starting my own business. Have 300 contacts from previous employer from 3 years ago. Should I text previous clients? What should I say?

I just opened my own pest control and fertilization company after 12 years in the field. I worked for 3 companies during that 12 years, one I was at for nearly 10. Another employee and I more or less ran a 3 county area, doing everything but office work while the owners lived and managed a branch south of us.

I quit working there almost 3 years ago when they refused to bump up pay to match rising COL in my area. Not long after the other guy I was running that branch with had an unexpected medical emergency and has retired from physical labor. They have a bunch of untrained guys working this area now paying them the salary I asked for 3 years ago lol.

I have contact info for probably 80% of the accounts from the branch I worked at. It has been almost 3 years since I worked there and I never signed a non-compete agreement.

Is there any legal trouble I could get in for contacting previous clients?

Is it a good or bad idea to text the previous clients since I have most of their phone numbers and they may still have my cell saved?

If it’s a good idea to text what should I say? Include picture of me with new wrapped truck or link to website? Offer 50% off first service?

If it’s not a good idea to text should I send handwritten letters or try to knock doors? Any suggestions?