More information you give to online retailers the bigger the risk.
I use both SIMs on my dual SIM phone, one my "long term" number I give to those who need my number long term the other I regard as "transient" and is a PAYG SIM with just enough balance to keep it active. "Burner" SIM number is used for online purchases and those who don't need my contact info long term so the number can be discarded without grief at any point.
Reason: several years ago a reputable company with an online shop that I'd used got hacked. Card number had to be changed quickly (card company took the "hit", several thousand). But then for next 2 years I was continually getting SCAM texts trying to get my new card details, easy to spot but a nuisance. But then the calls started, again easy to spot but over time they got threatening culminating in "Your address is <xxxxx> and we are going to come round and <yyyy> your daughter" - of course they were not but at that point I needed to report it to the Police and decided time to change my mobile number and that was really hard (many months later and despite ICO rules one NHS sub-contractor is still refusing to update my number on their records).
Ian