No, definitely not. 0870 numbers are business-rate service numbers which will cost money to call regardless of which O2 tariff you are on as you cannot use your inclusive minutes to make the call.
What are 0870 phone numbers?
Phone numbers which start with an 0870 prefix are used primarily as sales hotlines since Ofcom outlawed their use for post-sale customer service helplines in July 2015. Thankfully this means they are far less prevalent than they used to be but beware when calling a company to buy a product or service as they may still use an 0870 number.
Cost of calling 0870 numbers for O2 customers
Companies still using 0870 numbers will often quote the cost as “13p per minute plus access charge” which is technically correct, however this is misrepresentative of the total cost as the access charge may be significantly higher. For example O2 Pay and Go customers have to pay an access charge of 45p per minute, bringing the total call cost up to 58p per minute. Moreover Pay Monthly customers are even worse off as they have to pay an access charge of 55p per minute to call an 0870 number, making the full cost an eye-watering 68p per minute. It is therefore advisable to keep the call length down to an absolute minimum and to seek out cheaper alternatives to an 0870 number, such as local-rate 03 numbers or freephone helplines.