Data connexion can't work with battery under 30%

Hi everybody,

I noticed my phone could not get connected to the data network, obviously when the battery is “low” (if 25% or 30% can be considered as low). Meanwhile I cannot open or send MMS for example, it can be really bothering actually.
Is it normal?
I thought it could be a energy saving mode, but I could not figure out how to change that…

Could anyone help me with it ?
Thanks in advance !