Lebara roaming with iPhone 15

I've been with Lebara a few years using my old Android phone. When I went abroad, data roaming and mobile services would kick in virtually as soon as I took the phone off Airplane mode.

I bought a new iPhone 15, but every time I go abroad, it takes about 45-60 minutes for the data roaming and mobile to come fully online. Data roaming is the last service to come online. Once all kick in, they work perfectly. This is the same in the EU and India (so far).

My partner's Huawei fully kicks in as soon as she turns off Airplane mode (as mine used to do).

The settings are correct, and I turn the phone off and on again, but the time delay remains. I've contacted Lebara support, but they say it's a device issue.

Anyone else had the same issue?