Please check your bills twice before clearing them with clay telecom, because most of the times their bills are fake and tampered with. I had such an experience not very late, when I was using a clay sim for Bangkok. Everything was decent until I got my bill. I did not use data at all, how can I use data in a basic handset, but was charged around 100 THB for the same. My call timing were also doubled in terms of seconds to minutes. So overall they charged me over 4k for services I never used and increased call timing. Such services are definitely not acceptable and its left a bad taste for any future references