International Roaming Charges / Data Cap

Hello- I purchased an eSim for data roaming abroad (Peru) and have used 1GB of data from this. However, when I have checked my home ID SIM data usage in my device settings (by chance), it states that I have used 18.62 GB of data in 7 days. I don't know how this could have happened as I have kept my phone on airplane mode for most of the trip and just turned on data when needed to look for restaurants etc. I have a Google pixel 5a. Any advice on roaming charges, as the website states £15 per MB for use in countries not listed in the inclusion. I have calculated that the rate will be £279,600 according to the roaming charge. How is this possible? I have a cap on my account of £3 and have been told by the chat bot that this will have kicked in, so the most I would have to pay will be £3. However, this contradicts the information on the website. Any advice would be much appreciated, as I am travelling for the next 5 weeks and this is causing considerable stress given that I am not able to contact ID mobile via telephone and the website is currently down. Thank you in advance.