Happy Roam

I have the same issue as many before me. I bought a prepaid happy sim before travel. It was a $15 card and I topped up an additional $10. Purchased the 30 day plan for $15 and was left with $10 in my main balance before boarding. I landed in the US and rec’d multiple msgs about how my balance was at $3.10 and was too Low for data roaming unless I topped up. What is going on here? 

For info - I was on a 3 + 13 hour flight and only used wifi at the airport lounge during my transit as I couldn’t remember which PHL provider was the Happy provider. Now I have managed to TOP up another $10 as there is wifi at the SFO airport but I feel a little confused and aggrieved by this situation where I’m unable to connect to the roaming data that I had already purchased w/o having to TOP up my main balance again. 

Let me know what can be done to resolve this. Thanks.