LTE but no internet connection

I would like to ask how to fix this. Everytime I connect to our Wifi at home for a long time (like 2 or more days) and I connect back to my Mobile data there is no internet connection although it always shows LTE. This is the 4th or 5th times that it happened. Last time I called the Kunden Hotline and ask help, she told me to turn off my phone and remove the sim card, and I did...then my internet went back.. The next time it happened again and I called again, the same instruction was given to me plus she reset my account and it went back to normal again and I do have internet connection. Now it happened again… So everytime I lost my internet connection I should always call Kunden Hotline to reset my account????? And it will happen everytime I connect to our Wifi again and again and again.…