When you purchase a lycamobile prepaid plan, e.g. "to-all-xs", then on the corresponding web page there is no description of what happens if you don't renew the plan in time, that is clearly visible outright.
This most important information appeared to be hidden behind a spoiler "Terms and Conditions - National plans " in the bottom of the page, and currently it doesn't even mention mobile data. It only mentions phone calls: "Customers must keep the required balance to activate the bundle. Any calls after the bundle allowance, will be charged on the Standard rate."
So the bundle has de-activated unexpectedly, and the following top-ups sufficient to last for more than a month have been burnt in a few days by insane price for a MB of mobile data.
I must note that with some other mobile providers you can purchase a plan, and it doesn't de-activate just because you haven't paid on time.
The plan stays with you for a long time, and every top-up contributes to this plan.
So this whole experience appears to be highly unfair towards clients, and I don't even think it's legal, because Terms and Conditions do not mention mobile internet directly, except for roaming, which was not the case for me.
Update: the reply from LycaMobile has sent me to the same site that I've been quoting, without even referring to specific text. Thank you very much.
Well, I still don't see the exact information I've mentioned was missing.
I still don't think that hiding important information behind spoilers is a fair practice.
And for me it hasn't been obvious that the bundle gets disabled if you haven't paid on time, especially since I'd got used to better practice before.