Plan keeps upgrading on its own

[Ts524]

This phone/number is for my 10 year old daughter. I signed her up for the $25/month plan but for January and now April, the plan switched to the $40/month without any changes to the profile/plan in my account. 
Is there a way that she is getting promo texts that will automatically bump up the plan if she responds appropriately? We’ve looked at her phone after January and didn’t find any incoming promo texts but now I think she may have deleted it to try and hide it. 
Does anyone have a good explanation as to why the plan would jump from $25 to the $40/month? 
thanks. 

[porcupine]

yes you can as was stated earlier All it took was for the user of the device to respond yes for it to occur on the next renewal.

[HALIMACS]

@Ts524 

You're 100% correct.

Public Mobile has been sending 

promotional texts for plan upgrades in the last few months.

All it took was for the user of the device to respond yes for it to occur on the next renewal.

Adding:   you can change the plan back by logging into the self-serve account and go under the plans and add on section and selecting the desired plan. Make sure to schedule it for the next renewal.